I looked over the two air compressor cylinders and their pistons. The air compressor cylinder is a separate 7th cylinder, water cooled, located between cylinder 3 and 4 on the crankshaft. The A.C. jug from the locomotive had frozen and split. The one from the spare engine looked OK. In one A.C. piston all the rings were stuck. I had to purchase 2 oil rings for the best piston.
As it turned out the big end of the A.C. rod would not go straight through the hole in the crankcase. With 2 of the bolts removed and the rod at an angle it fits into the crankcase. I made 4 brass shims and 1 steel shim for the connecting rod. After several trial fittings I got the right number of shims in place. I was able to insert the A.C. piston in its jug.
