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Old 04-29-2013, 09:53 AM
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If you plan to use flat tops it would be a better idea as it'll lower the compression ratio enough to survive on pump gas.
With the overbore added in, head gasket, stock deck height, piston crown and stroke the ratio with 58cc chambers comes in around 9.7:1 which will work well on 93 octane as long as you have a good quench action.
Depending on how far down the piston is in the bore at TDC will judge the quench action. Lets say it's .025 in the hole at tdc. Then add in the head gasket thickness of .028 and we get .053 which isn't horrible. As long as it's under .060 your okay.
However if you were to use a thicker head gasket you'll lose quench action entirely and when the ratio is in the higher 9's you'll run into detonation problems unless the timing is set real carefully. A higher compression ratio is safer with a good quench action and without it the risk of detonation becomes greater.
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