how do you figure compression ratio?
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Joined: Sep 2006
Posts: 87
Likes: 0
From: Henryville Indiana
I'd be worried if your builder can't figure this out.
The compression ratio is a ratio of original volume of the cylinder to the compressed volume of the cylinder or volume at BDC vs TDC
Assuming a zero deck, .041 Compressed head gasket thickness, 65 cc heads, 3.75" stroke (383), 4.010 Bore (.010 over), & flat top pistons with no valve reliefs.
Head Gasket volume = ((3.14*(4.01^2))/4)*.041 = .515 Cubic Inches
Combustion Chamber Volume = 65 CC's * .061023 = 3.97 Cubic Inches
Cylinder Volume = ((3.14*(4.01^2))/4)*3.75 = 47.34 Cubic Inches
Volume @ BDC = .515+3.97+47.34=51.82 Cubic Inches
Volume @ TDC = .515+3.97 = 4.48 Cubic Inches
Compression Ratio = 51.82:4.48 or 11.56:1
You'll need to determine actual head gasket thickness/bore, cylinder bore, and piston relief volume to get a more accurate #.
The compression ratio is a ratio of original volume of the cylinder to the compressed volume of the cylinder or volume at BDC vs TDC
Assuming a zero deck, .041 Compressed head gasket thickness, 65 cc heads, 3.75" stroke (383), 4.010 Bore (.010 over), & flat top pistons with no valve reliefs.
Head Gasket volume = ((3.14*(4.01^2))/4)*.041 = .515 Cubic Inches
Combustion Chamber Volume = 65 CC's * .061023 = 3.97 Cubic Inches
Cylinder Volume = ((3.14*(4.01^2))/4)*3.75 = 47.34 Cubic Inches
Volume @ BDC = .515+3.97+47.34=51.82 Cubic Inches
Volume @ TDC = .515+3.97 = 4.48 Cubic Inches
Compression Ratio = 51.82:4.48 or 11.56:1
You'll need to determine actual head gasket thickness/bore, cylinder bore, and piston relief volume to get a more accurate #.
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,022
Likes: 30
From: Los Angeles CA
I'd be worried if your builder can't figure this out.
The compression ratio is a ratio of original volume of the cylinder to the compressed volume of the cylinder or volume at BDC vs TDC
Assuming a zero deck, .041 Compressed head gasket thickness, 65 cc heads, 3.75" stroke (383), 4.010 Bore (.010 over), & flat top pistons with no valve reliefs.
Head Gasket volume = ((3.14*(4.01^2))/4)*.041 = .515 Cubic Inches
Combustion Chamber Volume = 65 CC's * .061023 = 3.97 Cubic Inches
Cylinder Volume = ((3.14*(4.01^2))/4)*3.75 = 47.34 Cubic Inches
Volume @ BDC = .515+3.97+47.34=51.82 Cubic Inches
Volume @ TDC = .515+3.97 = 4.48 Cubic Inches
Compression Ratio = 51.82:4.48 or 11.56:1
You'll need to determine actual head gasket thickness/bore, cylinder bore, and piston relief volume to get a more accurate #.
The compression ratio is a ratio of original volume of the cylinder to the compressed volume of the cylinder or volume at BDC vs TDC
Assuming a zero deck, .041 Compressed head gasket thickness, 65 cc heads, 3.75" stroke (383), 4.010 Bore (.010 over), & flat top pistons with no valve reliefs.
Head Gasket volume = ((3.14*(4.01^2))/4)*.041 = .515 Cubic Inches
Combustion Chamber Volume = 65 CC's * .061023 = 3.97 Cubic Inches
Cylinder Volume = ((3.14*(4.01^2))/4)*3.75 = 47.34 Cubic Inches
Volume @ BDC = .515+3.97+47.34=51.82 Cubic Inches
Volume @ TDC = .515+3.97 = 4.48 Cubic Inches
Compression Ratio = 51.82:4.48 or 11.56:1
You'll need to determine actual head gasket thickness/bore, cylinder bore, and piston relief volume to get a more accurate #.
felpro 1003 4.166 .041 thick
mahle -5 cc pitons
4.030 bore which someone said was a 383 bore
Drifting
Joined: Dec 2005
Posts: 1,309
Likes: 20
From: Woodstock Georgia
