Quote:
Originally Posted by Quad
Butler Performance 557 Casting Budget Short Block Kit, 400 Block, 433-440 ci, 4.000" Str. These are rated by Butlers' for up to 500hp only. There was a thread not long ago that properly inspected & prepared 557's were good for 500hp.
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I know of one 557 based 400 that made 500+hp, but you’ll have to contact Tom S to find out exactly he had done to the block so it would survive at this power level. Replacing the main cap roll pins with solid dowel pin would be the first thing I would do along with a thorough NDT examination. A very light reciprocal mass would lower the stress on the bulkheads. Pontiac went to the 481988XX blocks in the later W72 400s for a reason.