Hy cff, the 637 V8 was developed from the V6s that came out in 1960, I believe it may be a 60 degree block. The 637 V8 has nothing in common with either the small or big block Chevrolet engines or any V8 engine developed by any of the other GM marques. The V6 engines ranged from 305 cu.in. to 478 cu. in., then the only V8 of that design the 637 and the largest engine of that design the "twin six" 702 cu.in. essentially two 351 engines with a common crankcase, hope that helps.
