I have been using a Tower 40 with an RJL diesel head. I broke it in as an glow plug engine according to the RJL instructions and put perhaps an hour's running time on it on the bench as a diesel (over a period of several years). Finally built an airplane for it. Put about 15 flights on it and the contrapiston in the RJL head came apart without damage to the engine. Visited the local engine Guru and got another bulletproof contrapiston made. Put another 15 or so flight on it and the crank broke, right at the crank web. Perhaps this was because of running it as a diesel with a two-oz Harry Higley heavy hub; which many will tell you neither is a good idea.

I ordered two new cranks from Tower and was most impressed with their service. I also picked up a NIB Tower 40 off ebay. I started to break it in as a glow and it would not start. It was obviously way overcompressed. Not having extra head gaskets, I took the head and went after it with my Dremel. I cut a bunch of triangular notches in the bubble of the combustion chamber, producing my new invention, the swirl-quench combustion chamber. This lowered the compression ratio sufficiently, and I broke it in. I took my old engine and lapped one of the new cranks in. The bronze bushing had gouges in it from removing the broken front part of the crank. Ran it once with the glow head to seat the crank and set it aside as a spare.

I made two flights today with the dieselized new engine and it ran excellent. Needless to say the spare engine and the extra crank will go along when I go flying, and I may pick up another Tower 40 off ebay. I guess I could be called bull-headed.

Jim