400 is usually considered fairly safe out of a 302, getting beyond that and you get into the questionable area. Over 500 and you're just rolling the dice. A huge amount of it has to do with the tune and how its used though. If the tune isn't right, or the motor is spun up too much, the block will crack open starting at the lifter galley and go straight down to the top of the main bearing journals. Most of this has to do with how much the 302 block flexes under heavy loads, which happens to be why the ones that get wound up real tight on a regular basis tend to pop head gaskets.
A 351 block on the other hand is usually considered safe up to 600-700 hp. They're just that much beefier.
A 351 block on the other hand is usually considered safe up to 600-700 hp. They're just that much beefier.
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