Originally Posted by cornerspeed
What exactly does drilled pistons mean?
Don: It means that instead of using the pistons that have the molded holes in them, they actually take one with smaller holes and drill the bigger holes in it.
ex: Instead of a 56 molded piston, they might take a 57 and drill it with a #56 drill bit.
The piston sizes are all based on the size of the drill blank for the holes...
What this does is create a *slightly* smaller hole (I think, maybe it was bigger) as the molded pistons have the holes molded into them and when the plastic cools the hole changes size slightly.