I have a question on engine numbers. I have two 1951 engines; I say 1951 only because they came from fairly original 1951 vehicles, recognizing that after 60 years, who knows what's original.

The first is a 235 ci engine from a PG vehicle. It has a block casting date of October, 1950, and a stamped number of HAD1239544. The "parts book" doesn't list a "HAD" prefix but a "HDA" prefix.

The second is a 216 ci with a stamped number of JAM1070225. Again, the "parts books" doesn't list a "JAM" prefix but does list a "JMA" prefix.

Is the parts book being taken too literally or is it really all that definitive? Is it likely that a October, 1950, cast block was originally installed in a 1951 vehicle? The 1951 cars were well into production when this engine was assembled.

Just a point that was made to me by another Chevy owner that I don't have an answer for.

Thanks for any clarification,

HAD is a 1950 Power Glide car engine
JAM is a 1951 passenger car 216 engine.

Oct 1950 would still be a 1950 engine as 1950 production ended on 11-11-1950
1951 production began on 11-20-50