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Effective volume on piston

3K views 14 replies 7 participants last post by  cobalt327 
#1 ·


I am trying to come up with an around about cr. These are the flat tops in my 355. I think the deck clearance is around .030. The guy at the machine shop said it is very possibly, he did not measure though. He also said with the 64cc Double hump heads, it is probably around 10.1 to 11.1. The motor is all the way together, running. So to late to measure now..lol What IS effective volume? And What do these look to you? Of course, you guys wont be able to give me exact numbers, just wanting around abouts.
 
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#10 ·
Yeah, youre like 9-1 or so....those 4-brow pistons have like 6 to 7.5 cc loss of volume....and with that large of a deck (.030) you are down quite a bit......unless the heads are shaved to the max and the chambers are like 62 or something w a really thin head gasket.....
 
#12 ·
You have a 1 point range of between about 9.2 and 10.2:1 depending on the block deck, gasket thickness and whether the pistons are 1.56" or 1.54" compression height.

The problem at the low end of the CR shown is the quench distance will be VERY wide (as much as 0.086" w/a 0.045 piston deck caused by a rebuilder piston combined w/an unmilled deck along w/a 0.041" gasket thickness).

As long as it'd not detonating, at least it shouldn't beat the bearings out of it or pinch a ring.
 
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