[Jay S]

Originally Posted by TransAm 474

Thanks guys, I assume the centered pins, instead of offset, in the aftermarket pistons wont present any problems? I noticed most all aftermaeket piston pins are centered.

It is fine. IRC, It actually increases the piston velocity some at tdc and helps the quench speed. More quench velocity is a good attribute. So is less contours on the piston top compared the the 4vr oems. FWIW, being that this is the high compression thread, our 510 cid 10.5 iron head engine I run on pump gas has flat tops with no valve reliefs and a small dish. The solid cam iron headed Pontiac we pushed compression on had oem forged piston reverse hung with the crank offset ground with a really tight quench. It was 10.4:1. It it probably had a higher piston velocity for the quench than an normal oem.

OEM’s do the offset to quiet down the engine noise some and moves the biggest forces past TDC slightly. It changes the dwell some as the piston is coming up on top dead center, moves the largest forces on the rod and crank over so the piston has more leverage on the crank. Seen different opinions on what it does with friction for what the engine is being used for.

The 2618 alloy of the icons takes more pistons to wall clearance. Engine will be noiser when cold than an oem forged or a forged 4340 alloy. 4340 (hope I have the number right) is a better alloy for your project imo. Builders run the icons all the time for projects like this though. They do have the best quench with out a lot of decking. Autotec can move the piston comp height in a 4340 alloy, so can Ross. More money though, can only say we did it.

I have built a couple engines that we reverse hung the oem pistons. Years back, was supposedly good for a couple horsepower and make pitch of the exhuast higher and louder. Lol, trying to intimidate the competition. I do not recall it changing much of anything though.

Better experts on here for piston than me, if I missed something somewhere feel free folks, correct it..