by Bruce Palmer III on Sun Apr 04, 2010 6:58 am
All 1944 produced crankcases, 45, 61, & 74, have this same combination of fours for 44 in the crankcase production number. You will find this combination of bottom numbers on all 1944 motors (except very-early 1944 which have late 1943 bottom numbers) and all early-1945 motors.
Of note, the first four in 44 of the crankace production number is the exact same four as used for the decade number (4) in all mid-1941 through early-1947 crankcase production numbers.
Also, from the offset between the decade 4 and the rest of the production number on the 1941-1947 bottom numbers that I have seen, I am led to believe that the decade 4 was stamped at an exact point in crankcase machining and mating with the rest of the bottom number stamped at a later point.