Now it seems there is a bit of a "update" in the controversy, according to David vizard, in some years past he tested the very idea of piston swapping, and his dyno test showed a gain of roughly 5hp, on a engine that produced 250hp. So you could assume, on a typical 150hp 318, it could be worth about 3, maybe 3 1/2hp, although the margin of error is likely more than that...I still say it's a waste of time, throw away your worn out 50+ year old factory pistons, bore and hone the block STRAIGHT and ROUND, and it will make MORE difference percentage wise than this hokey piston swap non sense. And dont use a carpenters level and flashlight to check your bores either.
