comp ratio

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Sep 24, 2009 | 12:28 AM

jlang

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From: klamathfalls

comp ratio

what comp ratio will i have with a stock crank and conn. rods (429) and the 413np pistons from federal mogoul i believe with the 12cc dish a .040 bore block and c8 heads wich i think are 72cc

i need to be up to 10:1 is this going to be enough or will i have to deck the block/ new pistons

Sep 24, 2009 | 12:37 AM

85e150

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Hhhm, more info needed. With a .040 head gasket the same diameter as your now-4.40 bore, 0 deck, & your other numbers, I get 13.78.

This is a 429, correct?

Put in your info here:

http://www.csgnetwork.com/compcalc.html

Head gasket thickness and diameter, and how far down the hole is the piston at TDC?

Sep 24, 2009 | 05:19 AM

monsterbaby

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From: iowa

Quote:

Originally Posted by 85e150six4mtod

Not sure what numbers you used to come up with that high of compression, but a 3.59" stroke, 4.400 bore, 12cc valve relief, 72cc chamber .041 thick gasket (typical felpro head gasket thickness) and zero deck ends up at 10.49. Leave the pistons down .010 and it's 10.25

Sep 24, 2009 | 01:14 PM

85e150

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I went back to the calculator above. Got the same results. Tried another calculator and got the same as you did.

http://www.rbracing-rsr.com/compstaticclalc.htm

So I went back and found my error. I used a positive value for the piston relief. I changed it to -12, and came up the same as you, at 10.49xxx.

Thanks for the correction.