i ended up with Hypereutectic pistons
in my .40 over engine.
there is a debate over forged verse Hypereutectic.
they say if your block is a little off from being over bored that forged is more forgiving.
but then they say there are disadvantages to using forged In that they are heavier, they are more limited in design, and the type of aluminum used. forged pistons are said to have a much higher expansion rate, which can make the break in for the engine harder. careful attention to the piston skirt clearance has to be applied. when the engine is cold the piston will have more slop in in it then a Hypereutectic because it expands so much as the engine heats up.
Hypereutectic pistons can be sensitive to total timing, any machining done to the bores has to be be REALLY close to spec also. but they do not expand as much and you don't get the piston slop on startup.
I think for a regular engine builder there is less to worry about if you go the Hypereutectic route, as long as the machining is good your fine.
i was worried about the slop/engine break in. and was turned away from forged pistons on a street car.
It really comes down to the skill of your machine shop and engine builder. I would recommend having the engine dynoed before you take possession of it from the builder, if he blows it up on the dyno better there then in your car.
