William Wynne

"The Corvair Authority"
5000-18 HWY 17 #247
Orange Park, FL 32003

Midwest Corvair Night Schools in Feb. 2005

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January 2005

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Bonus Photo

In previous Open E-mails, we've referred to development work on the details of the 601 firewall forward package. Above is a photo taken in our shop today of the firewall forward development and display stand. This is an actual factory 601 firewall, complete with the tricycle gear mounts. The Motor Mount is one of our production units. This week, we will work up a group of photos showing the installation of the gascolator and fuel pumps, and the remote oil filter housing and instrumentation. Watch for it in Open E-mail. We'll also post the specific dates and stops for our Midwestern Night School Tour.

Subj: Carburetor
Date: 1/29/05

Have you ever tried using the mixture control on a NAS-3 carburetor on a Corvair engine? If so, how effective is it? I can live without the cutoff feature; a simple fuel value will take care of that. In fact, I prefer this. I will miss the pump feature, but a primer will do. I have some concern about the negative G factor of a MA3-SPA in the event of a departure stall, especially with my 7 1/2 pound wood prop. I have one of each carb. Which one would you prefer in my situation?

Jack Nelson, Wagabond, Manual #5134, Livingston, Texas
Reply from WW:
The Stromberg and the MA3 are the two carburetors on which we have the most flight experience. The Pietenpol had a Stromberg on it for most of its flight hours, and the MA3 is what we use on the 601. It is true that the MA3 will quit if subjected to a solid negative G maneuver. But I don't think that you really have to be concerned about it unless you have an extreme airplane like a hand prop Cassutt with a 54" diameter wood prop. 95% of the typical Corvair applications like KRs and 601s, and certainly Pietenpols and Cub-type airplanes, will never notice this MA3 characteristic. The Stromberg is, by design, slightly more immune to this. You're correct that the Stromberg mixture control will not idle cutoff the engine, but it can be rigged for effective use and lean the engine through several hundred degrees, giving you several thousand feet more of altitude capability with correct mixture control. If choosing between the two carbs, I wouldn't let this characteristic define your choice. I'd probably go with the MA3 because its accelerator pump makes a priming system unnecessary in everything but the coldest environments.

Subj: Q Update
Date: 1/28/05

I'm rebuilding a Q200 into a TriQVair. Currently developing the motor-mount. Prototype to be tested soon. I own manual #5206 which I bought from you at your 2002 Oshkosh forum.

Jon M. Swenson, Golden Valley, MN

Reply from WW:
At Corvair College #7, our friend Joseph Snow of Ohio brought his Qvair firewall forward package, including mount and displayed it. At Corvair College #8, QVair builder Larry Koutz of Georgia also brought his motor mount and engine package to share. In attendance also was QVair builder David Posey, Georgia. David is working out a mount for his aircraft based on a Dragonfly design I did several years ago. These builders represent some of the more active QVair people, and I'm interested to see how their unique solutions to the motor mount evolve. We'll keep everyone posted.
Subj: Rebuild
Date: 1/27/05

What power loss if I use a standard 110 cam? Best way to straighten bent fins on the heads without breaking them? (Hot or cold?) I have a very low mileage engine and would think all lifters, pushrods should be fine. Valves are like new as are all the engine parts. EXCEPT FOR FLASHING in crankcases and the heads. I have never seen such rough castings on any engine. Crankshaft miced standard and not out of round. Cylinders are very clean but will rebore. Hope I don't sound cheap but I do have to be thrifty. Had crank magnafluxed and polished. Very nice. I watch your comments on Wednesday and Sunday.

I had one other question. Does Clark's regrind your old cam to make the OT-10 cam? Will they leave your cam gear in place? I hate to give up my cam that is already set to the crank.

Thank you very much, FRIEND BOB
Reply from WW:
The horsepower difference depends on what rpm you're going to run the engine at. It's about 5 at 2,800rpm, 8 at 3,100 and 11 or 12 at 3,400. If you're looking for an inexpensive alternative to a new OT-10, you can get a reground one from Clark's, part no. C8800R. They do all their grinding with the gear off. My understanding of accurate cam grinding is that it is based on the keyweigh location. I question how accurately it could be done with the gear still on. I'm very cautious about straightening bent fins on cylinder heads. You may want to warm them, but only with a propane torch. Yes, many people comment that the Corvair castings on the heads, especially, are far rougher than aluminum castings made today. But, as many internal inspections of core engines reveal, the quality was in the design and on the inside. We find many engines with virtually no wear inside due to the excellent design of the Corvair's oil system. The Corvair is a book you can't judge by the cover - or the reviews.
Subj: Pushrods
Date: 1/25/05

I am starting to clean up my engine and have the pushrod tubes out for painting. After general clean up, I notice that most of the tubes have small dents or deformities caused by pliers or wrenches. Most are very small but I am concerned. What condition are most tubes in that are used in the conversion? I would rather not replace them, but will if the small dents are a problem. They all appear straight and are the same length. Also the O-ring slots are in good condition.

Thanks, John Butterfield, 601XL
Reply from WW:
If the pushrods are as you describe, you have nothing to worry about, it's only cosmetic. It's not a big issue; when the engine's installed in the plane, you can't really see them anyway. As you point out, the primary concern is that they're straight, and have nice O-ring grooves. If you have any that are particularly bad, drop us an e-mail. We have about 500 used ones in the shop at any given time.

Subj: Fuel System
Date: 1/24/05

I've been looking at the new dual-pump system and was wondering why the following scenario wouldn't happen:

1. Primary pump fails
2. Fuel pressure drops and fuel pressure switch closes
3. Secondary pump starts
4. Fuel pressure rises and fuel pressure switch opens
5. Secondary pump stops
6. go to step #2

I thought it might work if the plumbing order was primary-switch-secondary. That way the fuel pressure switch would never "see" the pressure output from the secondary pump. But your photos show two pumps in series and then the pressure switch. What am I missing? Also which pump comes first (i.e. is connected to the gascolator): primary or secondary? A schematic (plumbing and electrical) would really help here.

Another scenario:

1. Engine stops and oil pressure drops
2. Primary fuel pump is turned off by oil pressure switch
3. Fuel pressure switch senses fuel pressure drop and starts secondary fuel pump

Now aren't you in the same bad situation the system was designed to avoid - heading for the ground with an active fuel pump?

A few other questions:
- what is the Facet model number of the pumps you use?
- where did you get the Nason pressure switch from? You published the make and model but I'm having a hard time finding a supplier.
- do you use the same make and model pressure switch for the oil and fuel pressure switches?

Thanks, Craig Payne, Utah, Manual #6154

Reply from WW:
You're confusing two different systems. The original mechanical/electrical system had a fuel pressure switch in the system. The electric/electric system on the plane now does not. In the photos on the 601 Web pages, the electrical device after the second pump is the sending unit for the electric fuel pressure gauge. In the electric/electric system, the primary pump is the first one after the gascolator. The system runs on this pump normally, and the other pump is a backup we only test during the run up and check periodically at cruise altitude. The primary pump is wired through the oil pressure switch as a safety feature. The secondary pump has no oil pressure switch in it because the back up system should have the least number of parts in it. The operation of the pumps is controlled by a 3-position switch labeled auto, off and backup. Notably, if you wanted to use an electric primer, you could boost the fuel pressure with the pump off with the backup pump at any time, engine running or not. Additionally, the backup position on the switch can be used to check the integrity of the fuel system during a pre-flight. We tend to publish wiring diagrams and schematics in Our Corvair Flyer newsletter. The 601 Web page is intended only as a visual guide to our work available to anyone on the Net. We reserve some of the most technical information for Manual owners, who are our direct customers.

The Facet pumps are available directly from the Aircraft Spruce catalog. They're the model that comes with AN-6 fittings built in. You may have a local supplier who deals with industrial engines and generators, or find a Nason source on the Web. If people have difficulty finding these, we'll make a quantity purchase and keep them in stock. The oil switch is the same make, but is a 15psi model.

In short, neither of the scenarios you're worried about can happen with the current electric/electric installation. Additionally, they didn't happen with the initial installation either, because the output pressure of the Facet pump was below the switch pressure intentionally, so that it would not cycle. Not a concern, just thought you might be curious.

Subj: Manual Supplement
Date: 1/24/05

I've obtained your Manual, videos, newsletters, etc. and find them to be great help. I was wondering if you have considered a supplement to the Manual that would feature the "latest and greatest" mods and current wisdom? Your lengthy history of research and development spans a great deal of time and modifications. It would be of great help if you summarized a current state of the art recommendation for your conversion in a concise shopping list so that those of us on a budget and buying a piece/part/section at a time can obtain the pieces we need with less confusion as to what is now considered to be the best solution. I realize you are in the business of Corvair conversions and mentoring those of us to do it ourselves, but the additional hints and tips of prepping the airframe/firewall to accept your conversion would be great, i.e. a simple line drawing of fuel line routing through the airframe to the gascolator, battery placement with suggested wire routing and wire size would be very helpful to me at this time in the building process. If some of these items are already addressed in your previous material please accept my apology. I've been reading and watching, but have been buried in trying to get the firewall back portion completed before focusing and learning about firewall forward.

Regards, Roger Parnow, 601XL taildragger - Corvair powered
Reply from WW:
We tend to publish the most up to date technical information in The Corvair Flyer. Of particular interest to 601 builders is this week's shop project: We're working on an exact 601 firewall and 601 Motor Mount on a stand in our shop. We're carefully documenting in notes and photographs every step of the installation. This particular installation will be built in its entirety in our shop. We'll then deliver and install it to Cleone Markwell's 601 in mid February. This will allow all 601 builders to follow along and we'll have the drawings you request available to our customers. We currently have all of them as hand sketches, but they're being updated to CAD drawings.
Subj: Fuel System on Your XL
Date: 1/19/05

Based on photos on your Web site, I've made some guesses about how fuel is routed from the wing tanks to the engine on your Zenair 601XL. One photo shows a tank selector valve on the center console below the instrument panel. Is there any risk having the fuel flow up to the valve and then back down to the floor and on to the firewall?

Other photos show your fuel pumps on the firewall. What little reading I have done on fuel systems says that with regard to preventing vapor lock, sucking is "bad" and pushing is "good." Some books recommend putting the fuel pumps in the wings next to the wing tanks. But I've looked at a lot of XLs and all of them put the fuel pump(s) up by the engine. Why is this a safe practice?

Craig Payne, Utah, Manual #6154
Reply from WW:
Theoretically, electric fuel pumps do a better job pushing fuel than they do pulling it. So, in a textbook, you would have the electric pump right at the tank. Conversely, here's the real world take: If it can be avoided at all costs, I avoid putting pressurized fuel lines through the cockpit. Just use your imagination to think about a pinhole leak in the fuel line and ask yourself where you want the fuel pump. Gus and I did extensive tests of the fuel pumps to ensure they wouldn't have a problem drawing the fuel, and would work in the series orientation in which we have them. To back up this testing, we also have about 130 hours on the plane. This is split equally between the first fuel system and the current one. The current fuel system reflects my own personal values on how the system should be installed. You'll notice I don't pressurize the gascolator either, and the gascolator is placed above the bottom of the firewall, where it wouldn't be smashed in an accident. While it's good to follow the textbook recommendations, the actual fuel system you fly will have to be optimized for your specific installation. I personally feel the one we have now is the best combination for a Corvair powered 601.

Subj: Carburetor
Date: 1/20/05

Ready to buy my carburetor for my soon to be turbocharged 164. I want to go with the Monnett Aero-carb. I had a brief discussion with them. They recommended the 35mm carb. Of course it will be upstream from the turbocharger so as not to lose atomization - correct? Do you agree with the size recommended? Sould I get the flange mount or spigot mount version? Thanks as always.

Terry Calderwood, Kitfox 7 Turbo, Missoula, MT

Reply from WW:
In a turbo system, if the order of components is carburetor, turbo, engine, this is called a draw through. The system you're mentioning, where it's turbo, carburetor, engine, is called a blow through. Original Corvair automotive turbo setups were draw through. Draw through is analagous to virtually all of the U.S. planes in WWII, which were carburetor, supercharger, engine. It is far easier to set up an engine and get it to run reliably as a draw through, thus all of my work with aircraft turbos on Corvairs will be draw throughs. Modern car turbo books discount this, but they don't understand the need for reliability in aircraft, nor the fact that throttle response in an airplane need not be as fast as a car. A 35mm Aero-carb would be a good size for a draw through. It absolutely should be a flange mount. I only use flange mount carburetors on aircraft. Spigot mounts have a dubious history of coming loose in some applications. Just to illustrate the complications of blow through systems, consider that if your turbo made 5 pounds of boost, it would blow the fuel backward through the carburetor and back into the fuel tank. Even if you installed a fuel pump, it would have to have a regulator diaphragm to increase the fuel pressure exactly as the boost in the engine built. There are many other complicating issues, but by comparison, the draw through will always produce a simplistic installation that works well.
Subj: Zenair 701
Date: 1/21/05

Hey, everybody. I know William has addressed the question of Corvair power for the Zenith 701 STOL. Zenith says the engine is too heavy. FWIW, I found this interesting comment on http://www.sportsplanes.com/zenith.aspx:

STOL CH 701 aircraft is being redesigned to meet the sLSA and eLSA standards. It was developed as an "off-airport" short take-off and landing kit aircraft to fulfill the demanding requirements of both sport pilots and first-time builders. First introduced in 1986. A new model is being developed for the sLSA and eLSA category. It will have higher gross weight.

Heard anything about this? Sounds pretty intriguing, especially if Zenith allows a little more weight in the engine compartment.

Russell Groves, Louisville, CO
Reply from WW:
I just took a quick glance at the Web site you mention, and I'm not sure these people are affiliated with the factory. Your question may be better directed to Sebastien at the Mexico, MO, Zenith factory. Just looking at the Web site, I was surprised to see a company that wanted to take deposits on the sLSA version of the 601, which hasn't even been built yet.
Subj: Wagabond
Date: 1/22/05

Haven't seen any updates lately regarding Dave's Wagabond project. Was wondering if any are forthcoming. Am also building a Wagabond and looking seriously at Corvair power.

Thanks, Jim Wegner, Manual #5146
Reply from WW:
Dave spent the weekend covering the tail surfaces on the plane. The public debut of the plane will be at Sun 'N Fun 2005. We'll have more updates as it goes to final assembly. December was a real busy month in the shop, and the plane didn't get a lot of attention. But Dave's been back on it steady in January, and it should look like an airplane by the end of next month.
Subj: NA-S3A1
Date: 1/22/05

I have a friend (Peter Johnstone) here in Australia who is presently trying a 40mm CV carb. While he plays with this, I have purchased a Stromberg carburetor NA-S3A1. I have the 35mm but you state that the 23 works well with the Corvair. Will the 35mm work with my Corvair? Your response would be greatly appreciated.

Also got my copy of The Corvair Flyer. Well done once again. You have stated that you are making Safety Shafts from 7075 alloy. Could 2024 be used in this application? I'm sure this will not be the first time this question is asked, so I'm trying to be the first. Hope to hear from you soon.

Darren, Aussie Corvair VP-2
Reply from WW:
The CV carb should work and run the engine, but keep in mind that these carbs have the characteristic of shutting down when exposed to ram air, and potentially stopping if they're subject to a diaphragm rupture. These types of carbs have flown on a lot of experimental engines, but they're not what you'd call simple and trouble free.

I think you have a typo here and meant to say a 35 and 32mm. In the U.S., these are generally referred to as 1 3/8 and 1 1/4" venturis. We have extensive flight time on both of these. The 32mm runs very nicely and will not restrict the power output of the engine until it's running in the 3,300rpm range. The 35mm will support any power output on a direct drive Corvair, yet it will idle smoothly and not load up.

We selected 7075 because it is as strong as many alloys of steel. While 2024 is fairly strong, I don't think it's tough enough for this application. We tested the 7075 to make sure it matched the strength we're looking for. You might get away with less, but I feel better with the far higher level of safety. If you're looking to make a shaft from the drawing, make it out of steel, not 2024.

Subj: Permatex
Date: 1/22/05

I know that you specify using Loctite 620 as the threadlocker of choice, but how about using Permatex High Strength High Temp Red? It's in all the automotive stores and readily available. Is this the same as 620? I thought Permatex was part of Loctite.

Thanks for answering these questions of mine.

Ralph Young, Zenair 601, Emmet, ID
Reply from WW:
Permatex and Loctite I believe are one in the same these days. 620 is in its own category for strength and temperature resistance, with gap filling characteristics. We've tested them all, and 620 has properties that blow away all other more common thread-locking products. We had used High Strength Red on the Safety Shaft and Hybrid Studs, but since we discovered 620, it allowed us to achieve excellent strength with head studs, and we've transitioned to using it everywhere we use thread-locker in the engine. One small bottle will do a whole engine. It carries my highest recommendation.
Subj: One more head stud question
Date: 1/19/05

Hi William, can you stand one more question about head studs? I need to replace the top studs due to thread corrosion (so far no case damage from removal). Your excellent posts on the subject have cleared everything up but one minor question. No mention is made of Clark's standard size replacement stud. Are they recommended? I know one of the selling points of the ARP stud was stretch similar to OEM or something like that. Would that be a concern with the Clark's studs? If these could be used (with Loctite 620) it would avoid the Helicoil/Timecert operation.

Thanks, Gunther Zion, Manual 5086, Greenfield, Indiana
Reply from WW:
We've put Clark's standard studs with Loctite 620 into Corvair cases which had no thread damage. With proper hole cleaning, they will perform as well as stock studs in excellent condition.

Subj: Bing carbs
Date: 1/17/05

I have been looking for an alternative to using the MA3 carb, mainly due to its cost. My question is: Would a Bing 64 carb with their new manual mixture control work for a 601XL Corvair application? I e-mailed http://www.greenskyadventures/ (in your neck of the woods - Florida). Jerry Olenik is the owner and he wasn't able to give me an answer since he is not familiar enough with the Corvair conversion.

Thanks, Ralph Young, Zenair 601, Emmet, ID

Reply from WW:
I have known Jerry for more than 10 years. He's an incredible expert on Rotax engines, and for a long time, was the oldest Rotax dealer in the country. I assume Jerry is certainly one of the leading experts in the country on Bing carburetors. Although the Corvair will run on a wide variety of carburetors, I don't know of anyone who's yet run it on a Bing or pair of Bings. To explore this option, you'd certainly need the guidance of an expert on the carb, and Jerry would be that person. Keep in mind, there are idiosynchracies to Bing type carburetors. They have the curious characteristic of shutting off if they're subjected to ram air pressure. In the end, I suspect that the engine would likely need two Bings to run, and the expense of these would approach the cost of an Ellison EFS-3A.
Subj: 1964 vs. 1965
Date: 1/17/05

I do not have your Manual yet. Just doing research at this time. I was given a YN motor, checked the crank and found out it is not the correct 164 cid motor. Have located another motor, ZF. Haven't checked the crank yet. My question: Are the 1964 110 motors as good as the 1965 and later motors. Heard there was a difference in the motors. Would like to replace the EA81 Subaru in my Zodiac with a Corvair. Have enjoyed reading about your Zenvair.

Regards, Dave New, CH601HDS, N928DN
Reply from WW:
Your ZF could be a 1964 long stroke engine with an 8409 crank, or a 1961-63 145cid engine with a short stroke 5607 crank. You should check that before purchasing it. The only difference between a 1964 and a 1965-69 engine is the width of the head gasket. In operation, we have never blown a head gasket on an engine that we've built. Thus, I have found the 1964s to be just as good as their later brethren. Keep in mind that we resurface the head gasket areas where necessary, and use solid copper head gaskets. Combined with using the correct torquing technique and pattern, you can expect the same perfect head gasket reliability we've experienced. All of this is covered in great detail in the Conversion Manual.
Subj: Turbo
Date: 1/17/05

Thanks for your last response. I noted your advice on setting up for the turbo when doing the conversion. I have a few questions before I decide on that approach. My primary use for the 601XL will be cross country flights to paved runways.

What do you expect as to the added performance with the turbo? Cruise speed, climb, additional fuel flow? I understand exact numbers will be available on your testing, but I would like an educated guess so that I can start ordering parts for the conversion. My thinking is that if the added performance is minimal, I will go with your standard conversion, but if I can expect significant improvement, the turbo mod would be my perference.

Also, you stated that you tested two turbo cams to make sure that the performance on a non-turbo engine does not adversely affect a non-turbo installation. I was not sure what your findings were.

Best Regards, John Butterfield, 601XL Corvair
Reply from WW:
I certainly want to emphasize that the standard Corvair engine and the XL are a good match and more than enough performance for virtually all 601 builders. Our takeoff roll at full gross is short, maybe 500 or 600 feet. On a standard day, the plane climbs about 700fpm, loaded. The additional power from the turbo would substantially increase the climb rate, but I've never really felt that the airplane needed it. Gus and Grace flew to Oshkosh at 9,500'. The plane was loaded to gross, and Gus reported that it still had a good rate of climb at altitude. The turbo would most likely be of interest to people with home field elevations in the 6000-8000' range. While most high altitude airports have long enough runways for a naturally aspirated engine, these airports are obviously in mountainous areas where sustained climbing ability is always a plus. My personal interest in the turbo is to see if the plane can deliver 165+mph TAS at 10,000' on 6 gallons per hour. These numbers are hard to predict, but I suspect they're possible.

Our tests on naturally aspirated engines with turbo cams installed showed that the engines were only slightly down in peak power, maybe 2 or 3% from the same engine equipped with the OT-10 cam. This is an acceptable reduction if you're interested in keeping turbocharging open as a later option.

Subj: Mains and Rod Journals
Date: 1/4/05

I suspect that I have a problem with my short block. I used Plastigage on the mains and rod journals. Mains .001 and rods .002. I put two bolts in the prop end of the crank and use a hammer handle to turn the engine over. Once it starts to turn it goes with much less effort and I don't feel any tight spots. I am concerned that when I get the cylinders and pistons on, the starter may not turn it over. Are these clearances too tight? I am using the .010-.010 reground crank that I got from you and .010 over size bearings.

Lynn Clark, Manual 5140, Chappell, Nebraska
Reply from WW:
The GM green Chassis Shop Manual has a section in the back called "Specifications." Section 6 is "Engine Mechanical." If you read the chart closely, you'll see that your clearances are close, but probably not too tight on the mains, and they are in the middle of the range on the connecting rods. When I see a reading that is indicating very little clearance uniformly on a crankshaft, I advise the builder to check it again and be very cautious not to move the crankshaft. If you bump it slightly while torquing the case, it will produce this effect. Engines that are assembled with STP and oil as a mixture may have enough stickyness that it takes 10 or 15 foot pounds of torque to get them to break loose, but they'll rotate with far less than that. If your #1 and 2 mains check out at slightly more than 1/1000, I would not be concerned. Mains numbers 3 and 4 can even be less than 1/1000 and the engine will operate perfectly.

Subj: MA3-SPA
Date: 1/13/05

Not knowing there were literally a dozen different "versions" of the MA3-SPA carb, I recently bought an "as removed" core 10-4895 which I have since found was for an O-300 Continental, not the O-200. If the carb body is the same, are there a few parts I can swap to convert it to a 10-4894 or can I overhaul it with a rebuild kit for the 10-4894, thus converting it to 10-4894 spec? Or should I try to trade-in/sell my 10-4895 and buy a 10-4894? Any other options?

Alan Lovchik, Spokane Valley, WA, 601XL tail feathers done, working on wings, 110 engine in a basket, Manual #6342

Reply from WW:
There are a number of internal differences between the two carbs. So while it may be possible to convert one into the other, it's not recommended. If you were going to work on the carburetor yourself or have a local A&P help you, you could sell your O-300 carb and get an O-200 carb. When we work on MA3-SPAs, I order the parts from Chief Aircraft. Chief's prices on parts are half of what most other sources are. On the other hand, if you were considering having the carburetor overhauled by a licensed repair station, you could ask them if they'd accept your O-300 carb as a core in lieu of an O-200 core. A high volume shop may actually value an O-300 core above the more common O-200 carb. Aircraft Spruce and other catalogs contain information on this, and have specific repair stations they work with. You can find more shops that specialize in this in the Trade-A-Plane newspaper. There's copies of it laying around virtually every general aviation airport. It's the yellow broadsheet that comes out three times a month. The MA3-SPA is an excellent carburetor for the Corvair. If it is within your budget to have one in good condition on your Corvair, you will certainly be well served by it. Stop and consider that it was the standard carburetor on tens of thousands of Cessna 150s, which logged millions of hours with amateur pilots. In all my years in aviation, I've not heard a single story of one of these carburetors letting down a 150 pilot.
Subj: Case studs
Date: 1/14/05

I'm in the beginnings of dissasembly and have thoroughly read the Conversion Manual. With regards to the case studs and removing the head nuts - the guy who sold me the engine (a local Corvair car enthusiast) recommended heating the studs with a propane torch over the length of the stud - just enough to expand the stud so that the nuts can be unscrewed by hand (with a socket of course). Questions: Have you heard of this method? Is this harmful to the studs or any other surrounding parts? Does it make the stud or connection to the case weaker?

I saw the open e-mail about the studs being rotated sligthly in the case if there is a large amount of torque put on them during head removal. It seems logical that this method could prevent that if it didn't harm anything in the process.

Thanks! Tom Brant, Brooklyn Park, MN
Reply from WW:
I had not heard of that method before, and to tell you the truth, I'm having a difficult time trying to picture it being effective. The main force that holds the nut on top of the stud is rust between the two. Heating the stud might relax the friction between the nut and the head, but that's not the issue. Your best method for removing nuts off the top row of head studs is to spray them over several days with a product called Kroil. It's an aerosol spray available from many sources, like hardware stores and airplane shops. It's possible to use an air impact gun to take off most nuts. If they're heavily rusted, use a 13mm 12-point metric socket, and tap it on with a hammer. Be careful not to exert more than 50 or 60 foot pounds of torque on the stud while unscrewing it. We use an air pressure regulator on our impact gun to keep from overstressing studs we're unscrewing nuts on. If you're doing just one engine, it's easier to use a half inch ratchet and take your time. If we have an extremely tough nut, I will ocassionally split it with a very sharp, small chisel. Hold the chisel parallel to the stud, and strike the nut end on, not sideways.
Subj: 8409 Crank
Date: 1/15/05

I am building a KR-2 and my Manual No. is 6344. I recently purchased a 1964 Corvair engine on eBay. The engine case No. is T0I05ZF (per Page 26 of the Manual, this should be ok). I just finished opening the top of the crankcase and found that the number stamped into the first crank throw from the pulley end was 5607 with 73B stamped on the opposite side of the throw. The opposite end of the crank was stamped GMT. The cylinder heads are no. 3813516. Given that I do not have an 8409 crankshaft, what is your opinion of my being able to use this engine in my KR? I have been able to remove one head and, except for a few stubborn stud nuts, am almost ready to remove the other head. I'm very anxious to hear from you.

Thanks! Bernie McLean, KR-2, Poplar Grove, IL
Reply from WW:
Unfortunately, you do not have a 110hp engine. What you have is a 1961-63 102hp engine. This is not a good candidate for an airplane conversion. If it was advertised as a 1964 110hp engine, get your money back. Also on page 26 of the Conversion Manual, it states: "On any motor which has a Y or Z in the code, you must remove the top cover and look at the crank. All 164cid motors have 8409 cast into the crank." A handful of people every year miss this. 5607 is the short stroke crankshaft. Although your engine says ZF, it has this in common with the 1961-63 engines. Additionally, you'll note the head number you noted does not appear in our list of approved heads; this is because it's a 102hp head. Although people in the past have flown 145cid engines, and they're certainly more powerful than any VW Type I aircraft engine, they are not good candidates from which to build a modern Corvair aircraft engine. 145cid engines actually weigh more than 164s. They have cranks that are not as strong, rods that are weaker, fewer cubic inches, and it's hard to find forged pistons for them. There are enough differences between the two motors that you should not purchase it part by part, but rather find a complete 164cid engine core.

Subj: Oil Pressure Sender Range, Air/Oil Separator, Oil Filter Mount
Date: 1/10/05

Sorry, I wasn't clear. I was asking about the sender for the oil pressure gauge, not the pressure switch for killing the fuel pump. I have a Stratomaster Ultra H "glass panel" from MGL Avionics that will display oil pressure from just about any sender. But I need to know the range of pressures the sender will have to cover.

I know I read a piece you wrote summarizing your testing of various air/oil separators. But for the life of me I can't find it. As I recall you concluded that the used Cessna part was still the best but that there was a new unit available from Aircraft Spruce that performed well. What is the part number of the Aircraft Spruce part?

In the Zenair 601 section of your Web site you recommend a Permacool remote mount. In the section on the new Oil System you recommend the Trans-Dapt 1045. Are they interchangeable? I can get the Permacool 1791 $10 cheaper ($21.88 vs. $31.75). Any reason for the change?

Craig Payne, Utah, Manual #6154
Reply from WW:
0-50 psi will cover any of the normal operating oil pressure scenarios in a Corvair. In our case, we always use mechanical oil pressure gauges. Although a lot of computerized instrumentation systems are attractive, I am partial to traditional gauges. When I built Lancair IVPs, we installed panels that cost more than $100,000 in some of the airframes. Even extremely high-end electronic engine monitoring systems in these panels had oodles of failures. Some of the more common affordable systems have had similar spotty records. They're undoubtedly far better than when we worked with the Archangel system years ago, but I doubt they'll win me over. Good luck with your system.

The Wicks Aircraft Part No. for their 5/8'' oil breather/separator is OIL-BS5/8. The Aircraft Spruce P/N is 10570. They both cost about $40. It works as well or better than the Cessna 150 breather we used for years. We modify Corvair valve covers by welding in 5/8" and 3/8" tubes. This is done on the pilot's side valve cover.

The oil filter mounts are identical, both the same Permacool part. I mentioned the Transdapt number because far more dealers handle them.

Subj: Dillsburg Tubing
Date: 1/9/05

On Page 90 of the 2004 Conversion Manual you say that Dillsburg Airplane Works in PA is a good place to buy 4130 tubing. I do not find their number in Sport Aviation. Could you send me an address and phone number?


Thanks. Max Butler, MANUAL #6448
Reply from WW:
Their address is Dillsburg Aeroplane Works, 114 Saw Mill Rd, Dillsburg, PA, Phone (717) 432-4589. If you're building an entire steel tube fuselage, it's probably worth ordering the tubing from Dillsburg. If you're just building a few small parts, it may be a lot easier to order it from Wicks or Aircraft Spruce.

Bonus Photos

Last Corvair Engine of 2004

R. David Stephens of Belpre, Ohio, above right, stopped by on Dec. 29, 2004. He came and observed the test run of the last engine we built in 2004. He liked it enough to buy the engine on the spot. It will be powering his Pietenpol in 2005. The engine is a very nice conversion with a number of our custom options.

First House Call of 2005

New Year's Day 2005, Grace and I visited Phil Maxson and his family in Washington, N.J. We made a couple of comments about how I have to be the only engine manufacturer in aviation who makes house calls. Phil built his engine in our shop in 2004. Since we were visiting family in New Jersey for the holidays, we took the time to stop by Phil's and check on his progress. In the photo above, Phil and I are replacing his stock oil filter housing with one of our new Oil Top Covers. The stock guide was pulled out using the threaded rod trick and a propane torch.

Here's a view of the development of Phil's 601XL tri gear. This is one of our standard mounts. The carburetor is an Ellison EFS-3A. Phil's airframe is largely done, with the exception of the canopy. Flying this plane to Oshkosh is well within the range of possibility.

A Very Sophisticated KR-2S

Above is a photo of KR/Corvair builder Stanislaw Jaglowski and Grace Ellen. A few days after visitng Phil, we drove over to see Stanley's project. He built it in a single car garage in Hackensack, N.J. We'd never met Stanley in person, just spoke to him on the phone and via e-mail. From his technical nature, I expected an outstanding project. These photos don't do it justice. It is simply the most sophisticated and detailed KR I have ever seen. Stanley is a mechanic and an engineer for a company that produces instrumentation and panels for airliners. He is a highly experienced commercial pilot from Poland who emigrated to the United States many years ago. His aviation background shows in every detail of his plane.

A quick glance shows that his plane is about 85-90% done. The woodwork is very clean. The plane is equipped with a sliding canopy with very smooth and positive operation. The empannage on the airplane is made of Kevlar skins. The engine is a Corvair, absolutely no expense spared, based on 88mm cylinders. The panel for the plane, shock mounted to be removed with four screws, is elegantly done to a very high standard. It includes a sophisticated GPS and auto pilot system. The fuselage is widened to about 40". Whereas some airplanes with a lot of modifications often strike me as just a collection of ideas, this one was notable because all of the work was extremely well integrated, making for one very impressive project.

We'll post more Bonus Photos from time to time to keep everybody in touch with developments in Corvair powered flight. If you have a photo you'd like to have appear here, e-mail us and let us know.

Subj: MA3-SPA
Date: 1/11/05

What is the part or serial # on the MA3-SPA carburetor that shows it came off an O-200 engine. There are a whole lot of MA3s out there and I believe you stated that the O-200 carb works best on the Corvair.

Thanks, Ralph Young, Zenair 601, Emmet, ID

Reply from WW:
The part no. of an MA3-SPA from an O-200 is 10-4894. It is by far the most common MA3-SPA. Although there are many other numbers, their production was small compared with the 4894. We've run other MA3-SPAs on the dynamometer and they don't run as cleanly as the one from the O-200. The one on our own airplane has absolutely no rejetting or resetting of any kind. We jsut took it off the O-200, cleaned it up and put it on the 601.
Subj: Thrust loads
Date: 1/11/05

Can't tell you how excited I am about the prospect of a smooth, reliable, and affordable 100hp range aviation engine!!!! Have yet to purchase any products, am curious about one subject area I didn't see covered anywhere on your Web site:

How are the thrust loads absorbed by the engine? Are there modifications to the main bearing assemblies? Or has it proved to simply not be a problem with lightweight propellers? I'm somewhat familiar with some VW conversions that go to great lengths to address this issue. Any enlightenment would be greatly appreciated. Don't know if this is covered in your Manual.

Thanks. shatley@cafes.net
Reply from WW:
It is covered in great detail in the Conversion Manual. But in a nutshell, the Corvair has an excellent double-sided thrust bearing from the factory. It has been flight proven over the past 45 years both in tractor and pusher configuration. In all my years of experimentation, flight and reasearch into the Corvair, I have not found a single case of an engine damaged by a bad thrust bearing. The bearing is actually on the opposite end of the crankshaft from the propeller. Although it is important to use either carbon fiber or wood props on Corvairs, and not metal ones, the thrust bearing would not be affected by the weight of the prop because of its opposite end of the engine location. Your question highlights one of the Corvair's advantages: Its long history allows great perspective, and means that no one using the engine today need be a test pilot or a guinea pig. Through our testing and information, you can follow a proven set of parameters and have an excellent expectation of success.
Subj: Head Studs, Paint
Date: 1/11/05

I have a set of case halves that came to me with two missing studs. The threads in the case *look* intact. Do I:

a) follow Clark's advice (pg 173) and try a stock, 0.003- or 0.006-over stud? If yes, which LocTite would you use: none, #262, #242, #243?

b) assume the worse and repair with Clark's 1 inch-long Time-Serts (#C8767L)? If yes, which LocTite would you use: none, #262, #242, #243?

c) other?

I have another set of case halves where some of the studs turned less than an 1/8 of a turn when I removed the head nuts. Are the "turned" ones safe? Others came out "clean" (no visible aluminum). Do I need to Time-Sert the "clean" holes?

Looking through the description of your rebuilding of accessory cases I am guessing that mine will come back in your "standard royal blue color." What paint do you use (and from what vendor)? I want to match it on the case halves and the cut-down bell housing.

So many questions :-)

Craig Payne, Utah, Manual #6154
Reply from WW:
If you did not personally unscrew the studs and observe whether or not they took metal, then you need to do a first class inspection. You could use a .003 over stud if you like, but we have had excellent test results with standard studs and Loctite 620 with proper surface prep. There's a lot of information on this in the previous Open E-mail. PLease note that when I say Loctite 620, I mean it. As good and useful as the other Loctite products are, they do not hold a candle to nor do they have the proper qualities to act as a replacement for 620. My comments on using stock size studs are only applicable if the proper Loctite is used, and used properly. You could use a time sert or a long helicoil as long as you re-form the thread on the stock stud. If you do not wish to reform the thread on the stock stud, you could always get an ARP head stud from Jeff Ballard at SC Performance. Our previous open e-mail details the thread patterns on these studs and why it is crucial that the correct thread pattern be used with the stock hole or a threaded repair.

On your second set of cases, again you can read a detailed explanation on the previous Open E-mail about how to deal with ones that unscrew cleanly. In my experience, a stud that turns 1/16 to 1/8 of a turn will not be a problem. Attempting to unscrew such a stud will result in a stripped hole about 25% of the time. If the stud looks good and is not damaged by corrosion or mechanical marks, I'd leave it alone. You could always double nut it and tighten it to 35 foot pounds of torque to see if it tightens into the case again the 1/8 turn that it backed off.

The color is Ford Dark Blue Part No. DE1606 by Plasticoat.

Subj: Tri Gear KR Mount
Date: 1/8/05

I'm in Gettysburg, PA and building a KR-2. I do have your Manual, but it's in the hangar with the plane. I'm getting ready to construct my engine mount and was told that since I'm installing the diel tri gear I must make some changes to it for the nose gear. I couldn't find anything in the Manual covering this. Can you assist me?

Thanks, Tim Boyer, KR2, Gettysburg, PA
Reply from WW:
Over the years, I've built 15 or 30 KR mounts to the design that Mark Langford and I worked out at Corvair College #3. About 1/3 of these were for tricycle geared KRs. These tricycle gear aircraft were set up for the Diehl nosegear. The Dehil nosegear has its own socket. The socket consists of a large diameter tube coming off a firewall plate at a 45 degree angle. It's stabilized by two smaller tubes, which in the VW application, are bolted onto the back of the engine mount. In our conversion, I cut off these two tubes and remove them from the main tube. They're replaced by two 3/4" .049 wall tubes that run from the same location on the main tube back into the clusters, where the upper tubes meet the back corners of the tray. There are good photos of this motor mount bolted onto a KR-2 without the engine in place on Mark Jones' Corvair/KR Web site. I built Mark's motor mount a few years ago. It was one of the first tricycle gear ones we did.

Subj: Moroso Blue Max Wires
Date: 1/9/05

Hi William, just a quicky. What is the part number on the Moroso Blue Max spiral wires you reccommend ? I'm gonna splurge on the good ones. Thanks

Terry Calderwood, 6419, Kitfox 7, Missoula, MT
Reply from WW:
The Moroso Part No. is 73225 if you want them in blue; it's 73217 if you want them in yellow; 73219 in red; and 73231 in black. Summit Racing is an excellent source of Moroso products. You can find them on the Web. Notice that these are eight-cylinder plug wire sets. The two extra wires provide you with enough material to make the leads for the coil switcher and two coils.

Subj: Stud Removal
Date: 1/9/05

I've read a lot of stud removal ideas. The Snapon tool is good (probably the best). But here are some ideas that work well on any stud. Double nut or triple nut if space permits; sometimes you have to use a thin washer to make the flats align to get the socket in place. Use a little discretion and if that does not work then clean and degrease the stud and nut and use red Loctite. Allow to set overnight or accelerate with a little heat (150-200F). This will almost always break the stud or it will come out. Breaking the stud is not desirable so stop and apply a soft heat to the casting if accessible. Follow up with your old candle trick or good grade of penetrating oil. Once the stud moves a small amount, then reverse direction a few times while applying more oil. In a lot of cases, this will prevent stripping the thread as it comes out. Use good grade 8 nuts (American made) and be patient. I have used this method for many years on both UNF and UNC threads to very large sizes (1 1/2 diameter and larger). It also works well to install studs as the Loctite can be softened by 300-400F heat, which will not damage the stud. William, I am sure you know all of this, but for the benefit of others, this is my 2 cents.

Ray Simpkins, Piketon, OH, Manual #5389

Reply from WW:
A bunch of good tips that we're glad to share with Open E-mail readers. During all discussions on head studs, I want to keep builders focused on the goal, which is to have a good set of reliable studs held in the case. Head studs were some of the first sophisticated tests that we ran more than 10 years ago. Our work on this and flight testing has been continuous, but the goal remains the same: Define easy and reliable techniques that builders can use only if they need to.

Follow this progression: The best case scenario is to find a completely assembled core motor which has no major corrosion on the top rows of head studs. In such a case, you can carefully disassemble the engine and, in all likelihood, all the studs will be good, and you can be reasonably assured that none of the studs were damaged if you did not use excessive torque to unscrew the nuts.

If any stud unscrews cleanly from the case during disassembly, inspect it carefully to ensure that it did not pull out any aluminum. A faint tinge of silver on the stud is acceptable, but if it pulled a few slivers, the thread in the hole should be considered damaged. In the first case, where it came out clean, the stud and the hole can be carefully cleaned with carb cleaner or Brake Kleen, and then the stud can be reinserted after being coated with Loctite 620. This Loctite will bond a stud in place which does not have significant drag torque on the way in. Just make sure that you have a good coating of 620 on the threaded areas, and that you set the stud to the same height as the other studs in its row. 620 is an amazing product that has gap filling capabilities and retains its strength several hundred degrees higher than regular Loctite. If you're only familiar with other Loctite, you're out of the loop on this one. We order ours from McMaster-Carr.

If you have a damaged hole where aluminum has been removed, you'll need some type of thread repair. Although this is covered in detail in the Conversion Manual, in a nutshell, you will either have to put a 3/8-16 helicoil or time sert in the case. Clark's Corvairs sells extra long versions of each of these specifically for the case. Drill the holes and tap them in a good drill press or mill. It's important that the hole go in as close as possible to vertical. Resist the temptation to hand drill it.

Once the thread insert is in place, you'll need to put the stud in it. All stock and oversize studs have a very special thread called a 3/8NC5. This thread is not compatible with helicoils or time serts. The appropriate solution with a stock stud is to rethread the bottom with a 3/8-16 split die, as detailed in the Conversion Manual. When done properly, this will minutely reshape the 3/8NC5 threads to 3/8-16. The alternative is to to call Jeff Balard at SC Performance and buy ARP head studs. These are specifically manufactured with the 3/8-16 thread, and are directly compatible with helicoils and time serts. Two notes on the ARP studs: You cannot use them in stock case holes because the 3/8-16 thread on them will not hold in the stock hole, which has NC5 threads. Second, because the 3/8-16 thread on them is straight and untapered, it will have no drag torque on installation. You will be able to screw them all the way in with your fingers. This is where the Loctite 620 comes into play, and will seal and bond these in. You just coat the threaded area on installation, and insert them to the correct depth.

If you're building a 2,900 or 3,100cc VW cylinder conversion, you cannot use helicoils on the head studs. There is not sufficient edge distance for them. Time serts are an option, but this is best done by your 3,100cc machinist, be it Ray Sedman at American Pie or the Wheeler brothers at Wheelerizing. Engines using Corvair cylinders can use any type of threaded repair. Very rarely do we ever use oversize studs in an engine. My testing has shown that a Loctite 620 stock stud threaded in finger tight in a stock hole exceeds the strength of a .003 or .006 over stud torqued in. If a stud unscrews and pulls aluminum chips with it, you need a threaded repair, not an oversize stud.

We have built, tested and flown every combination I've written about here. I have more quality testing experience on these thread repairs than anyone in the world of Corvairs. While bystanders may have differing opinions, invariably I've found it's based on some personal prejudice, and no actual testing. I did our research to provide a safe and reliable path for builders to follow, not to debate the subject with people who have no intention of ever building and flying a Corvair engine. Studs are a minor task on the way to building the engine that will power the airplane of your dreams. While some people will get bogged down or make a mountain of a molehill, the path to success is to just follow the information here and in my Conversion Manual, and call or e-mail us if you have further questions.

Subj: Roller Rockers
Date: 1/9/05

I was wondering if you can shed a little light on the roller rockers in you 601 engine. I'm about to start my engine re-build after 9 months of collecting and purchasing all the parts required. I purchased a set of roller rockers off eBay, the same as yours. I'm interested if there is anything I should be careful of.

I have new alloy rocker covers to clear the extended rocker height, longer rocker studs, new Isky valve springs, new valve guides and new stainless valves. The only thing that I have a concern over is the lengths for the push rods. What was the difference you found? Were they required to be much longer? What did you do and where did you purchase the extended push rod tubes?

Look forward to hearing your thoughts on this.

Regards, Darren Barnfield, VP-2, Australia
Reply from WW:
As you noted in your e-mail, roller rockers are not a stand alone item. They require polylocks, longer studs, deeper valve covers, and invariably, longer pushrods to correct the valve geometry. I'm pretty sure that our 601 is the only plane that's ever flown with roller rockers. We installed them not out of a sense of need, but to flight test them in order to be able to provide useful commentary on them. My primary thought is that they might reduce valve train wear or lower operating temperatures. Before flying them, I spoke at great length with Jeff Ballard and Ray Sedman. The consensus was they'll certainly do no harm, and testing will reveal what difference they make. As close as I can tell after 125 hours, I believe that they do not make an appreciable difference at our rpm. When considered as a system that costs $500-$600, I think the money would be better spent elsewhere on most builders' engines. For example, the same $600 could be used to upgrade from a Stromberg carburetor to a brand new Ellison.

Setting up the proper valve geometry is not a big deal for experienced engine builders, but it is a significant challenge for most homebuilders. Engines built with stock rockers and Corvair cylinders usually have very good valve geometry and almost always can run stock pushrods. Conversely, all the engines we've built with roller rockers or VW cylinders have needed some type of custom pushrod length. Our pushrods in the 601 were 3/16" longer than stock, and were provided by Ray Sedman at American Pi. He also provided pushrods that we used on other VW-cylindered engines that we built in 2004. Each engine required a different custom set. Not a big deal for us, but you can understand why I would recommend engines based on Corvair cylinders and stock rockers to 90% of our builders.

One more quick note: I am not a big fan of Isky valve springs. They may have been intended for a cam with far greater lift and duration than an OT-10. Jeff Ballard has sets of appropriate springs that we use in all of our engines.

Subj: Oil pressure sender range, Carbs
Date: 1/8/05

In your new oil setup, what range do I need on the pressure sender at the remote oil filter manifold? Or better yet what make and model of sender are you using?

What *available* carburetor can I use on my Corvair engine in a Zodiac XL? I'd use the Aerocarb but no one seems to be able to make it work in a pressurized fuel system. Just searching the Web turns up some nice $1600 carbs, but that seems disproportionate for a $4000 engine. Does the rest of the world flying Corvairs just happen to have a nice used carb sitting around?

Craig Payne, Utah, Manual #6154
Reply from WW:
Our 601 uses a Nason 15psi switch in the oil system. We are likely going to change this for a 10psi unit. Stewart Warner also makes a virtually identical switch.

Aircraft like the 601XL and a KR-2 without a header tank are unique in that they require a carburetor which can withstand fuel pressure. In my opinion, the two best carburetors for this are the Ellison EFS-3A, available brand new for $850, and a Marvel Schebler MA3-SPA from an O-200. A good used MA3-SPA is worth about $300. We overhauled ours with parts from Chief Aircraft, and we have about $450 in it. It performs flawlessly. There are any number of carburetor repair stations in the U.S. that will overhaul an MA3-SPA or sell you one outright. This can even be done through Aircraft Spruce, but you're likely to find better deals by reading the ads in Trade A Plane. Keep in mind that you must use an MA3-SPA from an O-200. It is by far the most plentiful model. Perhaps 75,000 of them were made. Last year at Oshkosh, I saw 40 or 50 of them for sale for less than $400. A number of our customers have called aircraft salvage yards and acquired servicable ones for less than $500. $1,600 is a complete extreme on the price of a carburetor for a pressurized fuel system. The Ellison is a first class option for half that. Steve Makish, Corvair/KR-2 pilot and leading customer of ours, has flown more types of carbs on a Corvair engine than anyone I can think of. For the past 50 or 60 hours, he's flown an EFS-3A Ellison on his plane and he loves it.

For builders who are using gravity feed fuel systems, the selection is wide open. MA3s, Aerocarbs ($400 new), and Stromberg NAS-3s ($200-$300 used) would be the most popular choices. Corvairs have successfully flown on Zeniths, Carters, Harley carbs, etc. We have tested an enormous range of carbs, and the engine is not particularly sensitive to specific carburetion as long as it is set correctly. The MA3 and the Strombergs have the advantage of being jetted right on the money for almost all Corvair engines. Others will require some adjustments. Thus, people with gravity fed airplanes have a great number of options for a few hundred dollars and down. I agree that $500-$800 for a pressure fuel system carb is not cheap, but represents a small fraction of the done cost of your airplane. On the day it flew, we had about $22,000 in our 601XL. I consider the $450 we spent on the carb a fair price for the flawless performance and certified reliability provided by the MA3-SPA.

Subj: Oil system questions
Date: 1/8/05

Hi William, A few oil system questions:

1) I live up here in the frozen North of Montana. We run 5W30 in our cars in the winter up here; the average winter temp is around 15 degrees. In the summer we may hit 100 degrees once. Castrol Syntech also comes in a 10W40 weight. Would it be more appropriate for me?

2) I found that Fram makes an oil filter for the Corvair, part number PH4. Can you use this in our conversion or is an external remote filter the way to go?

3)What oil cooler with AN-6 fittings have people been generally using. I've found some at auto part stores, JC Whitney, etc., but don't want to purchase without guidance.

Terry Calderwood, Kitfox 7, Missoula, MT
Reply from WW:
Your questions bring up the subject of integrated design. I use this term to refer to viewing the entire firewall forward package as a whole system, rather than looking at it piece by piece. Using your Kitfox 7 as an example, and discussing the oil system, I would recommend setting up your engine just like our 601 engine (with the exception of using a gravity feed fuel system). This means I would use a front starter and alternator, a 12-plate oil cooler in the stock location, and a remote oil filter setup using one of our Oil Top Covers and a remote oil filter housing on the firewall. A Transdapt 1045 housing will allow you to use any number of readily available filters that would have a self contained pressure relief. The housing is also the correct place for pressure and temperature instrumentation. An engine set up this way will free you from having any type of external cooler. Addtionally, our Nosebowl would be an excellent start on a cowling for your Model 7.

My extensive testing of oil systems indicates that 5W-30 is a good option for cold weather operation in Corvairs. We're currently using that same grade of Amsoil in the 601, even in fairly hot weather. Thin oil like this does a much better job of lubricating engines in cold weather starts. Pumping it is easier on the oil pump, and it has the advantage of never opening the bypass in the filter on a cold start, nor having an appreciable pressure drop across the filter. As you know, I'm not a big fan of many of the homemade rear start setups I've seen in the field because builders have ignored my warnings about creating excessive restrictions in their systems. It is not difficult to imagine thick oil, cold weather and bad design teaming up to starve an idling engine of oil flow to the rod bearings. Conversely, thin oil and good design will provide your engine with protection in the coldest weather.

Subj: Engine storage after conversion
Date: 1/7/05

I love your new ďOpen E-Mail.Ē Itís just what I wanted to see. Iíve already updated my files. I canít wait until the next string.

I just purchased a 1965 convertible Spider. Itís in above average shape with new carpets, seat covers and a top in boxes! The previous owner replaced the turbo engine with an RH engine, but included the complete original turbo engine & parts with the car. I plan to rebuild the turbo engine and restore it back into the car (that will be my practice engine). After that I plan to convert the RH using your Conversion Manual. I wonít be able to afford an airframe for a few years, but at least Iíll have an engine. I want a 601XL.

My question to you is, is there anything special that I should do to the engine when I build it so it can be stored for several years as I save for & build an airframe? I plan to store the finished engine on a basic auto-type engine stand, wrapped and sealed in plastic. I will store it in my garage/shop in Southern California, so there wonít be a great deal of temperature change or humidity to affect it. I read that I might not adjust the valves until ready to run it. Iíve had some ďcar guysĒ say that I should use grease rather than your oil/STP for assembly. Iím looking for a more reliable opinion. Iíll bet there will be other builders that build & store their engine before they build their airframe.

I enjoyed Corvair College 5 and my visit to your hangar in August 2004. Thanks Gus for the 601 ride! Is there a schedule for an up-issue of the Conversion Manual? If so, will there be a special price to upgrade my Manual #5876? Keep up the great work! I wish your attitudes would infect more businesses that I patronize.

Best to you all, Dave Thompson, California, Manual 5876, Wishing I was building a 601

P. S. Youíve got to update your pictures in the Zenith Aircraft Company Web site! Your 601XL is much too beautiful to not be shown in its finished state. (Just my opinion.)

Reply from WW:
Congratulations on landing a nice Corvair land-based project. Quite a number of guys who never thought about a Corvair car before caught the bug while searching out an airplane core. Dave Morris in Texas recently picked up a late model turbo car and Pat Panzera in California has a turbo coupe in his driveway to work on when his plane is done. There are many other examples, but the car certainly has a lot of appeal. Between Kevin, Gus and I, we own 8 or 9 land based Corvairs.

I would not use grease in assembling an engine, even one that is to be stored. Not all grease is oil soluable, and it's easy to imagine it clogging a filter or lifter, or restricting flow. STP and oil will cling tenaciously to machined surfaces. As an option, you could spray the external surfaces of the crankshaft, the rods, etc., with a can of ACF-50, available from Wicks or Spruce, before installing the Top Cover. It's the last word in preventing corrosion. You could take the option of not setting the valves, so that the ports are sealed, although I'd obviously advise wrapping the entire engine. We've stored engines for long periods of time, and if they're sealed up, they'll have no problems. Remember also that you will prime the oil pump on the engine before you start it, so you'll be flowing plenty of oil through it internally before it runs. If you wanted to be extreme, you could prime the oil pump intermittently over time, but I really don't think it's necessary.

We've always offered low cost updates to Manual owners who originally purchased it from us. At our option, I have frequently offered the same upgrade price to second hand owners. The main thing is we want to keep active builders updated with all the information at their fingertips. We balance this against an occasional request from a second or third owner of a 1996 Manual insisting he's owed a free update. We're friendly with everybody, and we expect people to be reasonable with us. With any major revision, we will offer a major discount to any original Manual owner. Additionally, we encourage all builders to subscribe to our newsletter, The Corvair Flyer. The Flyer is a 50/50 mixture of builders' success stories and technical information. A domestic Flyer subscription is $20 a year, but we offer numerous specials to Flyer subscribers to allow them to recoup the modest cost of staying up to date. We often hear that reading of other builders' successes in The Flyer is the motivator that gets people back in their shops and progressing on their projects. So it serves several purposes.

Speaking of visiting the shop, for 2005 we've organized Thursday-Saturday as the best days to visit the hangar. When a builder makes the trek to come all the way out to our place, we like to give them the full tour. Monday through Wednesday traditionally are the busiest days in the shop, where the full crew is working a 10-12 hour day. Thursday and Friday the pace is slower, and much more conducive to visits. Hopefully we'll see you again this year, but keep in mind that calling first is a good idea as we have a lot of road events this year.

I'll ask Sebastien to update the Zenith Web site. You're right - it would look better.

Subj: High Altitude Operations
Date: 1/7/05

I live out in the Rockies and expect to often operate my engine at 10-12000' cruise altitudes. My original plan was to use a CV carb from a Harley, but the specs for that carb state a 10000' maximum. Do you have any experience operating your flight engines at those kind of altitudes with the MA3-SPA carb? Any problems with mixture distribution or specific recommendations? Also, what about running a Corvair engine lean-of-peak, like I do in my O-320, for reduced stress on the engine and higher fuel efficiency?

Thanks, Andy Elliott, Mesa, AZ, Lycoming owner, Corvair wannabe!
Reply from WW:
Good to hear from you. Your e-mail is timely. It's two years ago this week we saw you at the San Antonio College.

Gus and Grace flew a 9500' cruise altitude to Oshkosh last summer. Gus reported perfect operation of the engine, and that it responded to leaning in an expected and normal manner. Recently a KR-2S flew to our place, and touched 14,000+ on the way. It has a 35mm Aerocarb (gravity feeding it from a header tank), and dislplayed normal operation and response to leaning. While I have not made an extensive study of lean of peak operation on a Corvair, preliminary indications and common sense suggest that what is applicable to horizontally opposed, certified air cooled engines also applies to the Corvair. One of the many benefits of the Corvair's configuration is that I have intentionally mimicked many of the features of certified engines, and therefore, operational experience is predictable and bears far closer performance to certified models than other alternative engines. Translation: It's a good thing. Just make sure you have good EGTs before really going after lean of peak operation.

Subj: KR-1 Cowling
Date: 1/6/05

Just a quick question, I've been looking for a KR-1 cowling for about a year, check Trade A Plane, Barnstormers all the time. NO LUCK. The plans I have are not very clear and hard to read. Any idea where I might get one that's already premolded or done. You can e-mail or call me collect here most of the time (retired).

Thank You for your time, Bill Sadler, Reno, NV, RENOSDALER@AOL.COM
Reply from WW:
We've put your note up on our Web site. We have a very big following in the KR community. Perhaps one of our builders will be able to help you out directly.

Subj: Fuel System
Date: 1/6/05

Hey thanks for your reply.

I'm using an MA-3SPA and, on your encouragement, recently ripped out my entire barbed fitting-based fuel plumbing and am replacing it with Earl's fittings and steel braided hose.

The fuel flow is: Main tank to Fram HPG-1 fuel filter to Facet pump to Header tank, with a return path back to main tank and also a vent in the header. Header tank to fuel shutoff valve, then via 3/8" aluminum tubing to bulkhead connector through the firewall to gascolator to Facet backup pump to Carb.

The flow from header to gascolator is entirely downhill. The gascolator does not extend below the fuselage bottom. The problem I have is getting from the gascolator to the carb without going uphill and then back downhill, because I can't get the carb very much higher than the gascolator due to the limited vertical space I have on the firewall.

I'm not so much worried about water as I am with fuel vapors migrating to the high spot in the reversal and blocking the fuel flow.

By the way, it looks like my business trip to Florida is going to be in early February now, and I have clearance from my boss to take some vacation time to make sure I can throw my engine in the SUV, drive down there, and spend some time with you guys getting my engine running after the business part of the trip is done.

Regards, Dave Morris, Dragonfly, Texas
Reply from WW:
Consider that we have run MA3s and Strombergs in both bowl forward and bowl rearward facing positions. Reversing the carburetor may give you better options on throttle linkage or fuel feed routing. In either case, you may take some of the up and down out of the line by routing it around the carburetor. Get a good look at all of the options for things like 180 degree full flow -6 ends. I don't think that you would have a problem with a vapor bubble in the line unless you let it get way too hot. You have the option of firesleeving the line to insulate it. I have not done this on any of our installations, and yet I have not experienced any type of vapor lock. Your fuel pump is an added plus on resisting any type of vapor situation. An MA3 by design, like other float carbs with vented bowls, is particularly good at passing vapor. In short, I doubt that you will have an issue with it. Before you fly the plane, you can block up the airplane at a high climb angle and run the engine on the ground with the airplane tied down. With zero forward airspeed, you'll produce the highest under-cowling temperatures, and it will be a fair test of the system's ability to flow on climb out.

Looking forward to your visit.

Subj: Your Corvair/KR Cowling
Date: 1/4/05

Rumor has it that you may be going to offer a cowling for the KR to use with the front starter??

Eric Pitts, Terre Haute, Indiana

Reply from WW:

Our latest issue of The Corvair Flyer newsletter has photos and a story on our Corvair powered KR project. Did you get your copy yet?
Subj: Fuel System
Date: 1/3/05

I'm plumbing my fuel system on a Dragonfly firewall, which as you know is tiny. I've changed my mind several times and ended up with the KISS principal, using a gravity feed from a header tank and a backup Facet pump in case gravity ain't enough.

Reading Tony Bingelis' Firewall Forward, he stresses that there should be no reversals in the fuel flow between the gascolator and the carburetor. I notice in your 601 fuel system, you've got the fuel flowing up from the gascolator through two Facet pumps then back down to the carb. That sort of configuration may be one of the few that would fit in my airplane, but I wonder if the reversal will make the system vulnerable to vapor accumulation or other problems associated with the high spot.

You've got a lot of flying time on different fuel systems, so what is your experience with that configuration? Are you able to do the reversal because your system isn't gravity-fed?

Thanks!, Dave Morris, Dragonfly, Texas
Reply from WW:
Tony Bingelis stands out as the individual who did more to improve the quality of your plans built homebuilts than any other person in the first 50 years of homebuilding. His magazine articles and four books are the standard for detail design information on homebuilts. Tony passed away several years ago, but most of his information is timeless. After 15 years of homebuilding, I could point to a few small items in his books that I'd disagree with in some circumstances. This doesn't mean Tony was wrong, it means that he was writing for all homebuilders, and seeking to define systems which would work in all homebuilts.

In some instances, the reversal of the fuel line is not an issue. Here's why: Think of the gascolator as a sink trap. If it's anywhere in the system, it will trap any water passing through that point until it is full of water. If I got more than a few CCs of water out of the gascolator, I'm going to drain a lot of fuel out of it and run the engine extensively to ensure the system is clear. If there were water in the reversal, you'd find it. One or two ounces of water going through a system will be strained out by a quality gascolator. If you have this much water in your gascolator, you need to stop and investigate before you go flying. My personal preference in fuel systems is no fuel lines in the cockpit under pressure, gascolator ahead of the firewall but above the bottom edge of it (this is especially important on an aircraft like a Dragonfly, which could break the canard in a hard landing and lay on its belly). Use a quality gascolator like the Andair. If you're going to use a fuel pump, it should come after the gascolator so the gascolator is not subject to pressure.

The main issue with the line between the pump and the carburetor is that it be a quality AN-style line, and have enough slack to allow for the movement of the engine. Preferably, you would firesleeve this line. This will give it additional resistance to heating the fuel with engine compartment air. Keep in mind that fuel has a boiling point around 170F under standard temperature and pressure. But it is significantly higher than this if it's subjected to only a few psi. If you're using a float type carb, the only real good candidate for a pressure system is an MA3-SPA. Keep in mind that once the fuel gets to the float chamber, it is no longer subjected to pressure, and its boiling point would return to 170F. In our airplane, the engine compartment air runs about 100F hotter than ambient. However, the MA3-SPA runs significantly cooler because the air flowing through it is outside ram air, and it has fuel vaporizing in it continuously while it's running. Write us back and let us know what type of carburetor you're thinking of using so we can discuss a few more details.

Subj: Turbocharging
Date: 1/3/05

Hi Mr. Wynne. I just ordered a Kitfox Series 7 and want to put a 164 cid Corvair in it with aftermarket turbocharging. I have your Manual and the Chassis manual. Can you advise/direct me to the info I need to build one. Obviously I need names of parts, specific engine modifications outside the ordinary for the non-turboed 164. I finally found an engine here in Montana. Boy it wasn't easy out here! Thank you very much.

Terry Calderwood, Kitfox 7, Missoula, MT
Reply from WW:
Not a lot of Corvairs found their way to Montana. I suspect it's easier to find 1960s pickup trucks in your state than 1960s cars. Glad you were able to track one down.

Kitfox Series 7 has a reputation as a well developed aircraft. A turbo 164 would likely provide outstanding performance while remaining within the weight restrictions for the aircraft. Our turbo testing is still undergoing detail work. But here is what we've established: Most important, the engine is clearly strong enough to take it. Second, it has enough cooling capacity so that cooling's not an issue. These are important points that stop other engines from effective turbocharging. The Corvair is the only production engine I can think of that was built to be turbocharged without the use of electronic controls on the ignition or fuel system, or a wastegate. These systems can be used to protect an average engine from hurting itself when turbocharged. Typically, however, homebuilt aircraft do not utilize these systems and it's better to have an engine of robust construction and plentiful cooling like the Corvair.

It should go without saying that a turbo engine needs to be a first class rebuild. It should have connecting rods with ARP bolts from Clark's or SC Performance. The cylinders should either be Clark's, or preferably, bored by Ray Sedman at American Pi. The rings have to be chrome. The exhaust valves should be stainless steel and have bronze guides. I'd be very tempted to have the seats and guides done by Wheelerizing in Brea, California. The only significant internal difference is the use of a TB-10 cam from Clark's in place of the OT-10 cam. This cam is a version of the OT-10 specifically for turbocharged engines. We have dyno tested this camshaft in two different naturally aspirated Corvairs to verify that it does not significantly reduce the engine's output when it is not turbocharged.

We still have to develop and fly several external systems to come up with a combination that is easy to operate, affordable and reliable. We'll be doing these tests in the coming months. The above recommendations are enough to go on to build your engine for now, and we'll supply the systems information as we further develop it.

Subj: 601 Cowling
Date: 1/3/05

Are you planning on putting out prints for cowlings to match the Corvair engine installation? I need to know how much overhang on the side skins do I need to leave?

Roger Parnow, 601XL Taildragger, Crestline, OH
Reply from WW:
We're currently working on prints for the sheet metal parts of the 601 cowling. These sheet metal parts go between the 601 fuselage and our Nosebowl. We made two prototype sets, and studied them for ways to make them simpler, lighter and easier to fabricate. The drawings will reflect these improvements rather than be simple copies of the prototype cowl on our plane. We're also going to offer cowling kits with all of the bending work prefabricated. We have an extremely nice Whitney industrial finger break in house, and will be able to offer these at an attractive price. The plans will be available free to anyone who's purchased a Nosebowl from us. We'll have pictures of the cowling kits on the Web site in a few weeks. Our own 601 has 2" on the sides ahead of the firewall. I've seen several builders' planes that are closer to 4" and would need to be trimmed later. Our intention is to leave the cowling long on the aft side to allow for builder variation. It's a very simple matter to trim it.

Subj: Oil Pan, Auto Gas
Date: 1/3/05

I have read your Manual for hours and am surprised how comfortable I am getting regarding building my engine. I have a core and have taken it apart. After reading about the mods you provide, I plan to use your system for the 601XL. I have completed my rudder and was pleased with the results.

My question is regarding the oil pan. I have what appears to be a good steel pan, and have a question regarding your pan. What are the advantages of having additional oil if cooling is not a problem? It seems that using the stock pan, and changing the oil more often would be an advantage for using the stock pan. Am I missing something?

For the future, I plan to use LL100, but if none is availabe, does it hurt the engine to mix auto gas with LL100, until you can get to a location where the avgas is available?

Thanks in advance, and am looking forward to begin ordering parts to complete my conversion. I still need to build the airplane, but am hoping to finish by July of this year.

Regards, John Butterfield, Zenair 601XL, California
Reply from WW:
Traditionally, Corvair engines used a modified stock oil pan for Pietenpol flight conversions. This worked and logged a lot of hours in Pietenpols. Many Corvair cores have damaged pans because it occasionally functioned as the skid plate on the car, and careless mechanics used it as a jack point. Because of this, few stock pans are good candidates for the traditional welded modification. (This mod is available in plans form from the Pietenpol family.) Today, the Corvair engines we build produce more power, and we expect them to last longer. Our oil system modifications are based on these points. Our Deep Sump Aluminum Oil Pans bolts right on and works with aircraft motor mounts. The additional oil capacity has the effect of making the engine run cooler, and extending the intervals between oil changes. The oil carried lower in the pan's sump allows the oil pickup to remain submerged in uncoordinated flight. For these reasons we install our Pan on every engine we build.

You can mix 100ll and 93 octane auto fuel. The engine can be tuned to run on 93 continuously. I have more than 100,000 miles of driving Corvair engines on the road, and this was all done on unleaded auto fuel. I prefer avgas in flight applications for a number of technical reasons outlined in great depth in the Conversion Manual, but people who have better access to 93 octane fuel can utilize it with minor tuning changes to the engine.

Subj: Little Wing Autogyro
Date: 12/30/04

I have recently become interested in the Little Wing autogyro. I am wondering if you have any direct experience with this machine. More generally, can a Corvair fly in an aircraft that can slow down like the gyro can? Ron Herron, Little Wing's designer and builder, e-mailed me saying his opinion is that the Corvair is too heavy and doesn't put out enough power for its weight, also that it overheats and needs a fan! (Maybe he hasn't had any recent experience...) Thing is, the radial he has on his single-place gyro weighs around the same as the Corvair, but it sits real close to the firewall. He has a two-place that is longer; builders have used the Rotax 914, the Hirth F30 and various VWs. What do you think?

Thanks, Jonathan Cartford, St. Paul, Minnesota, Manual 6417, no airplane, lots of dreams!

Reply from WW:
I have not followed the Little Wing extremely closely, but here's what gyro people who we're friends with share with us:

  • Being a tractor gyro, the Little Wing has many flight favorable characteristics that few pusher gyros can match. Tractor gyros are comparatively rare, and many of the things that people attribute to gyros across the board are not true of tractors.
  • Prior to the installation of the radial, Ron told everyone that any engine weighing more than 200 pounds was too much for the design. I don't know if he made any changes to the airframe, but many people saw a conflict between words and actions when he installed the R2800 radial. Your point that he may have zero experience with Corvair engines and be operating on parroted information is a good one. In my experience, a lot of good airframe designers are not engine guys and very few of them do any firsthand testing with engines. I strongly doubt that he has any personal experience with Corvair engines. Consider the theory about needing a blower fan. Prior to our work with Corvairs, this was a commonly held misconception. Anyone who reads our Web site can see that we've broken in and test run at very high power settings dozens of Corvair engines on the dynomometer; notably, these engines were pumping out this power at exactly zero airspeed with no blower fan. We've conducted break-in runs several hours long at continuous power settings above 100hp. This is all done with the cooling baffle on top of the engine and the prop wash. This isn't to suggest that Mr. Herron's a bad guy. Quite to the contrary, he has a number of admirers in sport aviation. I must agree with you that he's just not up to date on our work with the Corvair.

    I can assure you that a direct drive Corvair will produce more static thrust than a Rotax 912S. The 914, being turbocharged, is slightly heavier than the 912S and even more expensive. The Rotec radial is a beautiful engine, but again, it's astronomically priced. I haven't seen a Rotec on a scale, but I'm willing to bet a Corvair has a lighter installed weight. You could build three or four very nice Corvair engines for the price of either one of these imported engines.

  • Subj: Crank and Cylinders
    Date: 1/1/05

    I took my crankshaft to the shop and it has to be turned .030 under on the rods and .010 on the mains. I've heard several comments saying that using .010/.010 cranks are good, but don't believe I've seen anything on what the limits of a grind are. I see that Clark's has the bearings for them up to .030. Also the cylinders have a .005 taper. Would you recommend boring the minimum (.020) piston or going to .030 for a little larger displacement? I was discussing the crank grinding with the shop when I asked how far they recommended grinding the crank without going thru the nitriting or Tufftrided. He said that crank isn't nitrided anyhow....because it has some rust on it, and nitrided cranks don't rust. Is that correct? I suppose the nitriding was just on the journals only anyhow.

    Blue Skies, Bob Unternaehrer
    Reply from WW:
    Almost every Corvair crankshaft we've dealt with would be perfect if ground .010/.010. I have a lot of flight time on .010/.010 cranks. I'd be reluctant to fly a .030 under crankshaft. The availability of crankshafts for Corvairs is so good that I would get another which could be ground only .010/.010. .030 under might work perfectly fine, but that's a theory, not a flight proven fact. For building your own engine, I suggest you stay within previously tested limits.

    The nitriding on Corvair cranks is only a few thousandths of an inch deep. Most crank grinders will tell you that it is ground off by the time you do any type of work other than a light polish. The only Corvair cranks that were nitrided by the factory went into 140hp and turbo engines. Your crank grinder is quite wrong; I have several rusty 140 cranks in the scrap bin awaiting conversion to a mailbox post. The cubic inch difference between a .020 over and a .030 over engine is less than 1cid. That's roughly half a horsepower difference between the two engines, very negligible. In the past, the main reason we bored engines to .060 over was for weight reduction. They are three to four pounds lighter than engines with stock bores. .060 over adds 7cid to a stock engine, and makes a slight difference in power that we can actually measure on the dynamometer. If you have a 1964 engine, we recommend .030 as an overbore, and a 1965-69 engine can run .060 over. In the most recent Corvair Flyer newsletter, we have a bore vs. displacement chart for the nine most popular bores on a Corvair, and a discussion on the combinations and recommendations.

    Subj: Engine teardown
    Date: 1/1/05

    I'm in the process of tearing down, oiling, and bagging the parts of my core engine to preserve it for a future build. After removing all of the headnuts and rocker studs, the heads are still VERY stuck. I hit the heads as hard as I dared from every direction I could get at them using a block of wood and heavy ballpeen hammer, but they just won't come free from the cylinders. Do you have any hints or tips for getting them free without breaking anything?

    Thanks, Douglas Eatman, St. Augustine, FL, No airplane (yet!), Manual #6307
    Reply from WW:
    I'm glad you went straight from Corvair College #8 to purchasing a core. One of the reasons we recommend the best condition core engines for purchase is the fact that some of the more corroded or stuck engines represent a real challenge to disassemble. My gang in the shop have given up on only two engines in the past three years. With patience and perseverance, virtually any engine can be disassembled with minimum harm to the engine, your tools and your fingers. When a head is reluctant to come off, start by removing the pushrod tubes. Six pushrod tubes with dried out original O-rings can put a surprising grip on a head. Look in the Clark's catalog or Richard Finch's book to see what a pushrod tube removal tool looks like. Spray a lot of WD-40 down the sparkplug holes, and at the joint between the head and the cylinders. I use a block of hard wood and a 2 pound hammer to get the head off. Watch the joint between the head and the cylinders closely to ensure you're taking the head off square. If it's cocked at an angle, it's only going to bind up. Tap around the perimeter of the head in order to keep the opening between the head and the cylinder uniform and square. Keep in mind that many engines will want to stick the cylinders in the head, and have them slide out from the case. This is OK, but you may need to unbolt the rod caps if the respective pistons will not slide out the bottoms of their bores. Study it carefully and take your time. You may break a cylinder fin or inflict some other replacable damage. Don't be discouraged: Some engines are just a bigger challenge than others. Write back and let us know when you get it all apart.

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