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Can someone tell me how to figure my comp ratio? It's a standard bore and stroke 427 BBC (It hasn't been bored out yet). TRW L-2300F forged pistons and 92cc iron heads. Thanks in advance. I believe it would be around 10.5 if it's .060 over, but it's not, so I'm guessing the comp ratio is lower with a smaller bore. I really don't know.....I'm just guessing the last part.
 

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compression ratio

volume of one cylinder + volume of compression chamber+ volum of valve reliefs+ volume of head gasket+ deck relief of piston+ or - and dish or dome on piston, divided by the unswept area, which is all the area that is left when the piston is at top dead center.

EI:
volume of cylinder for a 427 = 878 CC
example combustion chamber =75 CC
example valve reliefs = 5 CC
example head gasket thickness of .040" X 4.3 " = 9.5CC
example piston relief from deck of block .030" X examp bore 4.25" = 7 CC Flat top pistons; no dish, no dome.

total CC volume= 974.5 CC

unswept area; 75 CC + 5 CC+ 9.5 CC + 7 CC= 96.5 CC

974.5 divided by 96.5 = 9.48:1 compression ratio

The combustion chamber, valve reliefs, gasket thickness, piston relief are examples only and not the actual figures.

The cylinder volume is also example, as I dont have your exact bore and stroke dimensions.
 

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Heres the specs I found on them. You will have to refigure for your heads. With 92cc heads it will be higher

SDPC Part Number: L2300F
Manufacturer: Sealed Power
Bore : 4.250"
Stroke : 3.760"
Rod Length : 6.135"
Pin Height : 1.767"
Weight : 828
Ring Width : 5/64", 5/64", 3/16'
Compression Ratio : 9.5:1
Pin Type (P/F) : Pressed
Dome Volume : 16.8

*Compression ratio is figured with 107cc heads.
 
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