[chiphead]

Originally Posted by ponchjoe

Yea, the 18cc 4.160 4032 pistons.

Did you measure final chamber size before you ordered pistons? I made that mistake on my original 400. Thought I had 72cc 670s, so I ordered 20 cc dish pistons for 9.2 compression with 3.75 stroke. Imagine my surprise years later when I actually cc'd the heads and got 77ccs! This was back in 2002-03 when I was led into the lower compression ratios and XE cams way of thinking.

For your 4.25 stroker motor, I ran the numbers. With 18CC dish, are you expecting 10.42 compression with 72cc (nominal) heads? That's too high for those 670s. That's perfect if you're going aluminum.

With high compression, you need at least a 228* intake lobe and 112-114LSA.