Originally Posted by BG383
Question: I have a crate 383 stroker (360hp/410lbs) on Sealed Hyperutectic Pistons(yields 9.5:1 CP, flat top, 2valve relief); GM Cast Iron heads (Valves: 1.94int/1.5exh)(72cc/170 runners)...Compressed Head Gasket of .041..Standard deck height..Comp Cams Hydraulic Flat tappet .477/.480 lift; 110 lsa; 224/230 dur. @0.50" Advertised Dur. 268/280. I want to run Aluminum Heads (preferable trick flow's, AFR, Dart) with 190 or 195 intake runners & 2.02/1.6 valves. What size Combustion Chamber should I use to keep a CP ratio of nothing greater 10.5. (Street Driven/ Maybe some Track car).....Thanks
Static Compression is Total Volume enclosed by the cylinder and head divided by the Compression Volume above the piston.
Total Volume consists of the sum of these elements:
- Cylinder Swept Volume (CSV), which is bore area times stoke.
- Piston Clearance Volume (PCV), which is bore area times the distance from the piston crown to the cylinder block deck.
- Head Gasket Volume (HGV), which is gasket bore area times the gasket thickness. The gasket bore is usually larger than the cylinder bore.
- Piston Head Volume (PHV), which is the positive or negative volume contained on the top of the piston. A dome makes a negative volume resuting a smaller compression volume and a higher ratio. A dish or valve pockets make for a positive volume resulting in a larger compression volume and a lower compression ratio.
To get at the answer you're looking for take the original formula and run it backwards to where Total Volume (TV) = Compression Volume (CV) times the Static Compression Ratio (SCR). TV=CV X SCR
Now take the Total Volume and subtract the volumes for the Piston Clearance Volume (PCV) plus the Head Gasket Volume (HGV) plus the Piston Head Volume (PHV). The result is the combustion chamber volume needed to get the SCR you're looking for.
Some handy conversion factors you'll need are 25.4 milli-meters (mm) to an inch and 16.4 cubic centi-meters (CC) in a cubic inch.