What should I consider when trying to achieve a certain compression ratio? This is not a daily driver (especially since the engine bay is empty!). I was shooting for a static CR of 11.75. Using the following values I come up this:

Cylinder Head Volume 57cc
Piston Head Volume 11cc (valve relief)
Gasket Thickness .054
Gasket Bore (in.) ? used 3.903
Cylinder Bore Diameter 3.903
Deck Clearance (in.) -.010
Stroke (in.) 4
Rod Length (in.) 6.125
Intake Closing Point (degrees) ABDC @ 0.050 lift (TRex) 47
STATIC CR 11.656
DYNAMIC EFFECTIVE CR 10.433

The dynamic seems awfully low. If I change the Piston Head Volume to 2cc (valve relief) I get:
Static CR 12.602
Dynamic CR 11.271

Is that too much static? I am trying to get the highest CR with out having to get custom pistons. 8 and 2 cc valve relief pistons are stock sizes.

 

Hmm, is this a stupid question and I just don't know it?

 

You need to use .006" timing figures to accurately figure DCR, not the .050 you used for intake closing point.

 

yeah, i dont think you would want your dynamic compression that high!

 

Hey BB, most guys go by static cr.Since you are using a rather big cam you can get away with that much cr. As more duration wiill bleed you cr at lower rpm's.I think you'll be fine!

 

I come up with 10.87 with 11cc dish and 12.11 with 2cc dish ! Thats stadic!!