Thread: 1955 Chrysler 331 Hemi build for '34 Plymouth Coupe

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Just my ignorance showing but you bored the block .060 over before you had pistons in hand? Has piston making gotten so advanced that now every ones' .060 over pistons are exactly .060 over. Just wondering. Beautiful work BTW.


Jack.

Originally Posted by Jack F

Just my ignorance showing but you bored the block .060 over before you had pistons in hand? Has piston making gotten so advanced that now every ones' .060 over pistons are exactly .060 over. Just wondering. Beautiful work BTW.


Jack.

Without boring it first, you don't know what size pistons to get. You normally bore the hole 0.005" shy of the finished size, and hone the last 5 out to achieve your clearance. When I say I bore it for 0.060" pistons, I mean I bored it to 0.055", and will hone the last 0.005" when I have the pistons. Piston technology and materials have gotten much better, and they are more consistent. And, before you say there are different clearances between cast and forged pistons, the piston has the intended clearance built into it. Ideally, you could bore to the numerical bore oversize, and it should be proper, but the best way is to hone to the actual pistons.