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ok, im doin a rebuild and need help on figuring my cr! i have a 4.04 bore, 58cc heads, 3.75 stroke (385 ci) and flat top pistons, no valve release, and my piston at tdc is .200 in the hole! so if i could figure out how many cc's .200" with a 4.04 bore is i could use that figure as my valve relief and figure my cr with a certain head gasket thickness. does this make sense? lol!
 

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out of work hair dresser
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With a gasket utilizing a 4.060 bore and assuming the use of "no" gasket period as per measurements, you've got around 8.85:1.

With the use of a .041 thick gasket with a 4.060 bore, you'll raise your CR a full point to 9.85:1 to 9.9:1.
 

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Discussion Starter #3
With a gasket utilizing a 4.060 bore and assuming the use of "no" gasket period as per measurements, you've got around 8.85:1.

With the use of a .041 thick gasket with a 4.060 bore, you'll raise your CR a full point to 9.85:1 to 9.9:1.

aint that backwards?
 

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out of work hair dresser
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Yes, it was correct in my head though. There was a communication problem from the brain to the keyboard. I have my best guys working on it right now.
 

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Beer me!!
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3.1416 x radius squared for area of a circle....
Then times by how far in the hole the piston is....
There are rougly 16.37 cc's in a cubic inch....

That should get you close to the volume of the void created by the piston being .2" in the hole. Be sure to add the volume of the valve reliefs if there are any.
 

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Beer me!!
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16.387 cc's in a cubic inch to be exact, so by my calculations, with a flat top piston, 4.04" bore, .200" in the hole, that would be 42 cc's.
 

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Beer me!!
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Dude it just occured to me, do you mean .020" in the hole rather than .200"? Two tenths is a long way in the hole with a flat top, your CR would be really low!!
 
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