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Thread: What is the compression ratio??
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03-24-2005 #1
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What is the compression ratio??
PROTC (a memeber on this site) has a 396 BBC bored to a 408 or .060 over!
It has the .550 dome forged pistons.. Supposed to yeild 11-1 compression with closed chambered heads.. (but he has open chamber heads)
anyone know what the compression is??Project JUST-N-SANE
84' Camaro Z-28, 355CID,9.0-1 compression, ATI procharger 9psi (over 650HP),T56 6 speed, 3.73 Motive gears! 11.70 at 122mph in the 1/4 while babying the throttle to keep the tires hooked ,with pump gas! (NOW INTERCOOLED)
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03-24-2005 #2
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You would have to know the CC of the heads and how far in the hole the pistons are to be sure.
True compression ratios for some pistons turn out to be significantly lower than advertisied.
But
As a reference... switching from open chamber to closed chamber heads on my BB mopar yeilded about 1 full point of compression increase.
So in your case, a rough guess? 10.1 compression.
Rob
03-24-2005 #3
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Do a search for compression ratio calculators.
Here is an example http://www.csgnetwork.com/compcalc.html
03-24-2005 #4
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Displacement= Bore x bore x Stroke x 0.7854 x 8
Compression ratio= (D + PV + DC + G + CC) / (PV + DC + G + CC)
D= Displacement
PV= Piston volume
DC= Deck clearance volume
G= Gasket volume
CC= Combustion chamber volume
03-25-2005 #5
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Brian, pull a valve cover and get me the casting number for the head and a date would be nice too. Then see if it still has the original engine code stamped in the pad on the block in front of the right head. Just write down whatever you find. I should be able to get you darn close.
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