William Wynne

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


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January 9, 2005

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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 also displayed 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.

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