As someone who has made and sold model airplane con-rods, 2024 is the best alloy, I've had a few 7075 rods break in FOX 36 combat engines, which are much harder on rods than a helicopter engine will ever be. 6061 will work fine in sport engines.
Both end s should be bushed with bronze, If I remember I think pin clearances were in the .001-.0015 range.
7075 and 2024 rods can be run without bronze bushings, if you hone the bore and get a decent cross hatch pattern. I have a few English 2.5cc diesels that have unbushed rods, and they typically have quite high bearing pressures.
Good luck |