Originally Posted by Horsepoweraddiction
i'm going mechanical roller and would i get more performance with a set of forged pistons ? i 'might' run a small nitrous set up.
Generally forged are heavier and run a looser piston-to-wall clearance. But there are lightweight (or lighter
weight) forgings that run tighter clearances than some of the old style forged pistons.
But there's little if any difference in the actual performance between the two if they are both set up properly- at least until the cast/cast hypereutectic piston reaches the point of no return, a point which will be found sooner than a forged piston. Just be sure to fully warm the engine up before hammering on it w/forged pistons. That gives them time to expand closer to their running dimensions where the ring seal will be better because of less piston rocking.
But if you plan on nitrous, forged gives a lot more leeway in case of detonation. Detonation can kill ANY piston when running nitrous, but a cast hypereutectic piston will literally shatter whereas a forging will tend to go down in one piece for the most part unless the detonation is ignored. And it may
even survive if the detonation isn't that severe.
Nitrous is very demanding on an engine. Aftermarket rods might be in order because I do not know of anyone who has been satisfied w/a "small" shot of N2O. At the VERY least, the rods need to be magnetic particle inspected, new ARP hardware installed, and then resize them. There are ignition boxes that will pull out timing to keep the engine safe; if I were to build a serious nitrous engine, you can bet I would be running one. Not really necessary at the lower levels, but even then the timing can be run higher when not using nitrous- which equates to better performance when on or off the bottle.
When you get to the >250 HP stage, think about better rings/ring material. Even at low doses, plasma moly is the minimum because moly inlay can chip off the ring. 250 HP and up forged isn't an option IMO, although you'll hear guys who get away w/it. Trouble is there's NO leeway if the tuneup is off, or a fuel pump problem comes up or for any number of things.
This barely scratches the surface but will give you some things to think about. There are guys here w/more experience using nitrous than me, hopefully they will be along shortly.