I feel that the 375 HP limit mentioned in a couple posts is reasonable for a "557" block. Remember that's a 100% safety margin for the original design parameters give or take a few HP. These were designed for 185 HP and 4500 RPM's. So likely good for the 375 HP level and 5000 RPM's for an occasional blast on the street. Unless doing a numbers matching restoration, I would bypass that inferior casting for the much better ones still out there. JMO.
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