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Small Block Unit Numbers :: 1964 - 1990


Small Block Unit Numbers


4 Bolt Mains

Except for experimental and ultra-exotic [Mondello, Dave Smith Engineering, etc.] custom setups, there is no such thing as an Olds 4-bolt block or main caps [455 or 350, etc.]. There were never any made.

Oversize Lifter Bore

With any block, watch out for the 'O' stamp on the lifter bore boss, indicating a 0.010" oversize lifter. Either Oldsmobile would only have stock 0.010" over replacements or THERE ARE NONE AVAILABLE. Which means you either get to sleeve the lifter bore (difficult and expen$ive), or scrap the block, or, re-use that old lifter. Resleeving the lifter bore is not fun.

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