Calculating Compression?
09-20-2010, 12:47 PM
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Calculating Compression? i'd like to forge my bottom end 
the engine will get a blower on it and i'd like it to be ready for it so with that being said here are the specs: 347CI (stock crankshaft that'll be turned) and i need it around 9:1 compression, stock rod length. so with 67CC heads would i need a 22cc dished piston? or can someone show me how to do it?
the engine will get a blower on it and i'd like it to be ready for it so with that being said here are the specs: 347CI (stock crankshaft that'll be turned) and i need it around 9:1 compression, stock rod length. so with 67CC heads would i need a 22cc dished piston? or can someone show me how to do it? 
09-20-2010, 01:24 PM
#2
http://www.csgnetwork.com/compcalc.html
There's a decent online calculator if you want to mess with it.
There's a decent online calculator if you want to mess with it.
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Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
09-20-2010, 02:09 PM
#3
Assuming...
Cylinder Head Volume (cc) 67
Piston Head Volume (cc) 13
Gasket Thickness (in.) 0.051
Gasket Bore (in.) 3.905
Cylinder Bore Diameter (in.) 3.910
Deck Clearance (in.) -0.005
Stroke (in.) 3.622
STATIC COMPRESSION RATIO
8.986:1
This will greatly change with deck clearance and gasket thickness. Find something close to that or larger and you can change your gasket thickness to accommodate what you find. IE 16cc dish pistons with a 0.035" gasket would put you back at 8.999:1. Just look for something close to 13 with your bore and use one of the calculators in this thread.
There are many good calculators. This is the one I use.
Cylinder Head Volume (cc) 67
Piston Head Volume (cc) 13
Gasket Thickness (in.) 0.051
Gasket Bore (in.) 3.905
Cylinder Bore Diameter (in.) 3.910
Deck Clearance (in.) -0.005
Stroke (in.) 3.622
STATIC COMPRESSION RATIO
8.986:1
This will greatly change with deck clearance and gasket thickness. Find something close to that or larger and you can change your gasket thickness to accommodate what you find. IE 16cc dish pistons with a 0.035" gasket would put you back at 8.999:1. Just look for something close to 13 with your bore and use one of the calculators in this thread.
There are many good calculators. This is the one I use.
Last edited by 1SLwLS1; 09-20-2010 at 02:17 PM.
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09-21-2010, 01:13 AM
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