Re: Question on my 1937 Twelve's Engine Number

Posted by Owen_Dyneto On 2014/4/28 22:29:10

It would be really nice if someday an index to all the engine suffixes surfaced, I've never seen one. An "A" suffix would have an entirely different meaning from one year and/or engine to another; for example one year and on one engine it might mean a change from a forged to a cast camshaft, another year the same letter might indicate a change in valve guides or some other entirely different feature. I'm uncertain of the meaning of an "A" suffix for 1937 Twelves but think it might be a running change in piston type. The 1937 Twelve started using a tin-plated aluminum alloy piston with a simple expansion strut, and by 38 the Twelve used a 0.006" cam-ground tin-plated aluminum alloy piston with an autothermic strut. But that's just guesswork on my part, someone else may be able to positively identify the significance.

As in almost all the prewar engines 1939 and back, pistons were selectively hand-fitted and letters were used to identify under and oversize pistons; in 1937/38 A, A-A, B, B-B, C, C-C, D and D-D were used for this purpose but these were marked on the pistons themselves and not as a suffix to the engine #.