The pistons and connecting rods were different in the two engines. The engine from the locomotive was 10 years older and had cast iron pistons. The donated engine had aluminum pistons. I was not able to get all the old pistons out and decided to go with the aluminum pistons. Trouble was there were only 5 connecting rods for the newer pistons. I had to modify an aluminum piston to work with one old style connecting rod. Bronze bushings were made and pressed into the piston so the piston pin could pivot in the piston.
