William Wynne

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


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January 16, 2005

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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?

P.S. THANKS FOR THE QUICK SENDING OF MY GREAT STUFF!!

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.

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