OK here's the deal. I have misplaced a note book and it has an equation in it that I need. I am getting ready to figure the static compression on an engine that I need to screw back together. I haven't CCd the heads yet but I hopefully will in the near future, so I don't have all my info yet. Anyway one of you must have the equation I am looking for. I know that I need swept volume + deck height+ compressed gasket thickness etc. Does someone have that equation for me? please?
Yep that one will do it, I would still like the equation for those times when I am not near a computer (I like running the slide rule to keep my brain sharp LOL) but that will get me to the same place. Thanks for the quick answer.
Not a formula as such, but I can lay it out; (***uming inches for bore and stroke) Bore area = π * bore²/4 swept volume = bore area * stroke deck volume = bore area * depth of piston at TDC (negative if above deck) gasket volume = gasket thickness*π * gasket bore²/4 piston top volume, CC of dish and valve pockets or dome/16.387 (positive if dish, negative if dome). Head volume, CC of head/16.387 Clearance volume = deck volume+gasket volume+piston volume+head volume compression ratio = (clearance volume + swept volume)/clearance volume If you want to get finicky, you can also add the clearance volume between the piston and bore diameters down to the top ring, but that's usually pretty small.
I probably won't need to get finicky. LOL a tenth of a percent won't change my outcome much. Basically I need to ballpark static ratio to work toward a general fuel requirement. When I get that far I am probably going to need to lower compression just enough to be able to tune for pump gas. The plan is to stay on the ragged edge so that I can uptune for better fuel and quick short bursts of speed. Its a sort of a balancing act as I am sure that everyone is aware. Now to add this to one of my notebooks that I can locate.
The Jalopy Journal
