Stuart_Snow

I don't have the exact numbers of currently flying engines but I can say the "Corvair Movement" has become quite popular in the experimental aviation world. Perhaps 500? I'll have to do some research on that. The engines best suited for conversion are the 64-69 164 CI ones. They use a GM 8409 crank which had longer throw to increase displacement from the early 145CI. The case has small indentations inside for clearance. Preferred heads are the 95 and 110 HP non-smog heads which have a quench area. this helps create the turbulence needed in the combustion chamber to ward off detonation. Smog heads do not have this quench area and are not used. The ignition is not dual as you would normally expect on an aircraft engine running two plugs and dual mags. It is dual in the sense that there is a primary crane and secondary points unit in the distributor which can be switched by the pilot. The two coils use a coil switcher if one fails. This type of setup has proven to not be a problem for reliability. Since this type of setup uses extremely high voltage racing coils and plug gaps are at .035 this produces a very efficient ignition spark given the relatively small bore size of the corvair. Plug fouling is unheard of with he corvair but does happen with magneto aircraft engines using narrow plug gaps. Most aircraft engines have very large bore size which requires the two firing plugs for efficient combustion. Successful corvair pilots are using traditional aircraft carburetors like the Marvel Schebler or Stromberg that provide a rich mixture at full power. Detonation is always the enemy that can creep up if things are not set up right which is the reason for the forged pistons. I intend to run 100 Octane in mine since I have flat topped pistons and am using the 110 HP heads. Other piston/head combinations provide more margin for detonation using lower 93 octane fuels. The corvair has the advantage of 6 cylinders, is smooth running and can still fly well on 5 cylinders. The aircraft is mostly spruce and plywood with fabric covering but uses a lot of chrome-moly fabricated parts and fittings. I'm enjoying learning how to weld the thin walled chrome-moly tubing with my small victor torch. Your welding tutorials using low pressure and small tips are helpful as heat management is critical. I certainly did a lot of research before I was convinced that using the corvair is a reliable option. I have found that successful pilots using corvairs are the ones who follow Mr Wynne's formulas to the T since he has spent his whole life doing the testing and development and is willing to teach others. It sure was rewarding to take a grimy junkyard hulk and turn it into a running flight engine. I'm thankful for people like yourself and Mr Wynne who are willing to teach and pass on knowledge.

Here are some photos of the Corvair aircraft engine conversion for my Pietenpol Air Camper project. The Air Camper was designed by Bernard Pietenpol in 1929 and used a model A ford engine originally. Later Pietenpol was the first to use a Corvair engine in his design. My engine is based on the conversion design and parts developed by William Wynne at flycorvair.com and Sport Performance Aviation flywithspa.com. It is a bored out .030 2.7 Liter (164 C.I. originally) 100 HP engine. 3.0 liter versions are also popular using other piston/cylinder combinations and a 3.3 stoker option is available using SPA's billet crankshaft. My engine uses original cylinders with forged pistons. A 5th bearing and crankshaft for prop loads designed by SPA. A modified oil assembly with high volume oil pump and oil filter adapter. Reworked and modified heads by SPA include welded on intake tubes, deep hardened seats and stainless steel valves. All the original corvair fan and blower equipment goes away and traditional aircraft cooling ducts get used. The ignition is a modified distributor which has points and a crane electronic unit and two coils. The advance curve is modified to come in early and total advance is 32 degrees. These modifications have been tested and proven by Mr Wynne over the past 30 years. The corvair has proven to be a very robust and reliable flight engine and has a reputation for smooth running. I call it my Tonawonda Tornado.

My CJ re-builders manual has arrived and I have had a chance to do some reading and thinking about where I want to go with this project. Since this jeep is still all original and untouched by any modifications I will do a quality rebuild of the 258 and keep it OEM. It has served this jeep well for the past 40 years after all so why not go for another 40. I will do a standard .030 re-bore with new pistons. The bores look good but have some wear as do the piston skirts and gummed up oil rings. Best to start from scratch after 118K miles. The rod bearings and journals look great which backs up my theory that this jeep was babied most of its life. I have experience with the older carter 1 barrel on my 54 F-head so that is a plus. This one looks only sightly more complex and was working when the jeep last ran. I had entertained the thought of the Comp Cam 252 but I'm not sure what the Carter 1 barrel would think of that and may open up a pandoras box. I could use some advice here as my gut feeling tells me I would need an upgrade of my fuel/air intake system to see any gains. This jeep has the Prestolite distributor with the BID (breaker-less inductive discharge) module. This may be an area I will look at upgrading. Is this the weakest link for this engine? I think I read that it is not the best option however it appears to have worked so far. I could use some advice here. I share your IMG_0271.MOVon keeping the engine bay as simple as possible for back country use. This is one reason I have treasured the CJ3B on many remote hunting trips and this was a factor in my decision to not do a stroker or EFI at this time. I'll get this project rolling but have a daughter to get married next month $$$. This project also came along in the middle of an airplane building project. I have spent the past several years converting a 1964 Corvair engine into a safe and reliable Aircraft engine. It sounds crazy but it was done under the guidance of William Wynne at Flycorvair.com. It runs now and I'll post a video if I can. The airplane is underway but is a long term project. I'm not a professional mechanic but this drives home the point that its all about how much you are willing to learn. I'm enjoying the site and I value your experience. I made some very costly mistakes on the F-head rebuild several years ago taking shortcuts. I learned my lesson the hard way that time. IMG_0271.MOVIMG_0271.MOV

My Restoration manual is due to arrive this week. I couldn't wait and was able to extract the engine and get it on the stand. Starrett gauges are standing by. So far it looks sound and turns over easy after setting for several years. I found no pieces in the oil pan! I'm looking forward to examining the bores and crankshaft. It turns out the head was redone by the same gentleman and WWII vet that did my CJ3B head. It just sat on the block for several years and never got bolted on. If I send the block out for machine work I'll make sure it is decked properly.

Moses, Thank you, I'm glad I found a good resource for re-build info. This jeep appears to have been well cared for by the original owner. The odometer says 18K miles but I'm sure that is 118K. I think a lot of it was road miles between Phoenix and a Mountain cabin. It doesn't appear to have ever been off-roaded very hard. No desert pinstripes or rock strikes underneath. The key to finding this jeep was having the CJ3-B. I wasn't looking for another jeep but while driving the 3B one day I was approached by someone who said they had an old jeep at their place they wanted to sell and I should come see it. I said OK not expecting much. What I found was this faded out CJ-7 with no doors and the head off do to a blown gasket. It had been setting for over 10 years and the head bolts and push rods were lost along with a lot of other nuts and bolts from the engine compartment. He wanted $1500 for it which I though was not bad given the condition but didn't buy it. After about 3 months the guy called me again and asked if I still wanted it. I couldn't refuse this time and drug it home with he 3B. I do have the smog pump and everything that goes with it and the Carter 1 barrel carb which looks rebuild-able. I will pull the engine out and go through it to see what I have to work with. I think it will be serviceable based on the condition of the rest of the jeep. I will have to meet Arizona emissions so I'll consider my EFI options and mild HP improvements for running up these mountain grades we have. I'm glad I've found the right place for good technical advice. Stuart

I saw this CJ-7 in a barn and it attached itself to my CJ-3B recently and followed me home. I didn't know what to do so I joined this group. I only know how to work on F-heads. I started rubbing on the paint and now its shiny again so I'm going to be forced to make it run now. The head is off and all the parts are in the back. I don't know anything about these modern jeeps (1977) so I think I will need the re-builder's guide. It has a 258 with a 4 speed (granny?), a Spicer 20 transfer case, Front disk brakes, Non-power steering. Factory side mounted spare. Original factory paint (Tawny Orange). Solid floors and minor rust spots under the doors which are missing. It has and EGR/Air guard emissions system but no converter. Since this jeep is a one owner Arizona jeep I'm going to have to make it run again. I dont know why this had to happen to me but I'm hoping this group will help get me up to speed on the 258 engine. Stuart