Wanting to Raise the Compression

730 Views 4 Replies 3 Participants Last post by demonstang76, Sep 1, 2011

demonstang76

Discussion Starter · Aug 31, 2011

Alright guys i want to make myself 100% clear on this before i start buying stuff i cant use and this site hasnt let me down yet

I have a 65 289 block and bottom end, with hyper. flat top speed pro pistons with 4 valve reliefs (+8cc). i have ported 302 D0OE heads with 2.02 and 1.6 valves (i was told 60cc combustion chambers). Im installing a X303 cam(.542 lift). By the looks of the heads with the 2.02 intake valve i highly doubt it could be milled down anymore. if it was the head, if sat flat, would sit on the valves lol. so im wanting to get the compression ratio up too at least 10:1 in order to do that with the gasket and pistons i have i need to drop at least 4cc's of combustion chamber to get too 10:1.

Now with all that said anyone have any experiance with pistons i could change too that will give the 2.02 valves enough room to open but raise my compression a little? Just so everyone knows the engine is currently in a car with heads so i cant get the dimensions of the valve reliefs or piston clearance myself. any ideas at all will be appreciated Thanks in advance

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cindys_sn95

· #2 · Aug 31, 2011

damian, i hate to burst your bubble but looks like no body else is going to step up. this is a bad idea. IF your chambers are 60cc you are already at or about 9.5-9.6, with a iron head and HYPERPATHETIC pistons....this is not good. the hyper pisons are very brittle and pron to breaking under detonation. why are you wanting more compression anyway?

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demonstang76

Discussion Starter · #3 · Sep 1, 2011

thanks for the much needed bubble burst cindy, apparantly i had an urge to split my 289 down the middle. i went back and looked and i need alot more then 5cc to push 10:1, i entered +8cc on dome volume and relief volume, i actually am more around 8.5:1 right now and only way im gonna get that many cc is to redesign my piston and heads setup, no thanks lol

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TOM RENZO

· #4 · Sep 1, 2011

If i were you i would DITCH the hyper pistons. They SUCK. Then work with dome heights and cam selection. Never figure compression ratios before deciding on a cam. they work together.

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demonstang76

Discussion Starter · #5 · Sep 1, 2011

Hyper pistons sounded good in high school when i was doing the low budget rebuild for a senior project, sadly i wish i was aware i would have came out cheaper just to get forged to begin with. i looked at the numbers on dyno sim, with all my information perfect im still looking just over 350 to the fly with lower then stock compression... ill manage somehow

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