Rebuilding an Aerovee Engine

We finally finished rebuilding our Aerovee 2.1 engine. We learned in Oct. 2010 that a crack had developed in the case and a new case was needed. This meant for a complete engine tear down to swap all parts to a new case. When I finally went to go remove the engine from the plane I looked closely and could barely see the crack. It’s obvious why I missed it before. The photos below illustrate my partner Joe and I removing the engine from the airframe, put it on the back rack of my SUV, taking it home to my garage, and breaking down the engine, painting the new engine block, and re-assembling the new engine, then taking it back to the airport.

This was my first “complete” engine rebuild from start to finish. It was actually super easy with the only difficult part being closing the case and keeping the crankshaft on these special dial pins that hold the bearings in place. That took 3 hours to do something that really should only take 5 minutes.Then I had to find a way to torque the rear gland nut on the crankshaft to 217-240 ft/lbs. My torque wrench doesn’t go over 150 ft/lbs. So I used basic math and put my 200 lbs of body weight on a breaker bar 13 inches out. This resulted in 233 ft/lbs at the nut. I had to bolt the prop flange to a 2×6 which was also bolted to my workbench (see photo below).

The new engine block arrived with various modifications made by Sonex to the case. They machine the case, and welded in a few places. However, you still have to file and sand certain parts as it is still a case made from a mold in Brazil. It’s obvious they mass produce these cases.

It’s standard to paint the case. There are two ways to paint the case. One is with engine block enamel which you can find at any auto parts store. The other way, which I tried out this time, is to mix oil based paint with gasoline. You mix it at a 50/50 ratio. This makes it capable to withstand high temperatures. It’s pretty thin, and more like staining, but it adheres well. The engine case shouldn’t exceed 150 deg. I also will be doing this to the cylinders. They shouldn’t ever exceed 400 deg. Keep in mind that my typical cylinder head temperatures are 340-350 deg even in blazing hot Dallas.

AeroConversions (Sonex) recommends that the engine be setup with an 8.0:1 compression ratio. This is perfect for running 100 LL avgas. The engine ‘can’ run 92 octane auto gasoline, but not unless the compression ration is below 7.6:1 (7.0:1 is best). If auto gas is run in this engine with an 8.0:1 ratio then pre-detonation may occur. Since all kits they send out are exactly the same they are able to provide a simple formula for figuring this out. I followed their formula, but also double checked it with the full compression ratio calculation

[Swept Volume + Deck cc volume + Head cc volume] / [Deck cc volume + Head cc volume] = Compression Ratio

The swept volume is 545 cc’s (2180 cc’s divided by 4 cylinders)
The head volume is 55 cc’s
The deck cc’s is 0.13 (deck height was 0.00″ with 0.13″ in shims added)
The deck volume was 21.962 cc’s (92 x 92 x 0.13 x 0.01996)

[545 + 21.962 + 55 = 621.962 cc’s] / [21.962 = 55 = 76.962 cc’s]
= 8.0814:1 compression ratio.

The engine ran again for the first time on December 22, 2010. There was confusion over ignition timing as the manual was wrong by 180 deg, but once we figured that out the engine ran great! I think I have a bit more power and RPM’s than before. Currently just checking up to makes sure the whole thing is running good. So far so good!

The photos go in chronological order from start to finish (top to bottom).

Comments are closed.