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Old 03-19-2012, 02:29 AM
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need someone to calculate compression ratio please

Can someone please tell me what the compression ratio is for a 454 chevy with a 4.280 bore x 4.00 stroke, with a 2 valve relief piston with a .090 dish, .024 below deck surface, 118cc heads, and a .039 head gasket please.
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Old 03-19-2012, 04:50 AM
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Quote:
Originally Posted by tchapps88
Can someone please tell me what the compression ratio is for a 454 chevy with a 4.280 bore x 4.00 stroke, with a 2 valve relief piston with a .090 dish, .024 below deck surface, 118cc heads, and a .039 head gasket please.
Need to know the volume of the piston dish. Might find it by the part number if you don't know it, or by googling it. You can get semi-close by measuring the diameter of the dish and figuring the volume by using the formula for the volume of a cylinder: pi x r2 x h .

Then plug all your numbers into a calculator like this one. Pay attention to the signs of your numbers as explained on the calculator site; different calculators vary on what sign represents a dished piston volume, for instance.

Last edited by cobalt327; 03-19-2012 at 04:56 AM.
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Old 03-19-2012, 09:51 AM
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Its going to be very low. Time for a supercharger.
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Old 03-19-2012, 11:27 AM
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Very low- like not even 7.5:1 w/a dish of 13cc or bigger...
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Old 03-19-2012, 12:47 PM
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Quote:
Originally Posted by tchapps88
Can someone please tell me what the compression ratio is for a 454 chevy with a 4.280 bore x 4.00 stroke, with a 2 valve relief piston with a .090 dish, .024 below deck surface, 118cc heads, and a .039 head gasket please.
With all that info, and assuming 8cc for the piston (7cc for valve reliefs and 1cc for the dish), that comes out to: 7.69 : 1
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