That is not a casting number. It is the engine serial number stamped on the pad just to the rear of where the distributor goes into the block.
228 is the engine size in cubic inches. All of the smaller GMC trucks used 228 engines from 1939 through 1953. The following digits are a sequential number of 228 engines starting in 1939. The "A" at the beginning means the engine left the factory with slightly oversized pistons and undersized main and rod bearings. The machining process wasn't as accurate back then.
Here is the magic decoder ring for that leading letter.
Last edited by Bill Hanlon; 01/22/20243:21 AM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
The block's casting number is on the other side of the block, along with the casting date.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
