What is my compression ratio?

[434 nova]

I think it is 11.1 compression but i dont know for sure here is my engine specs let me know what it is.

434 sbc, flat top je pistons 2 valve reliefs, 4.155 bore, 4.000 stroke, 6.000 rods, 75 cc heads, 41. thick head gaskets, the pistons are in a dart little m block built by ohio crankshaft so it is a 9.025 deck. Thanks for the help.

[supernova]

I'm going to need the cc's of the valve reliefs, the bore of the head gasket also. Then I can give you an accurate #.

[434 nova]

5cc on the flat tops and the head gasket are 41 cc and bore size 4.190......... Felpro 1004

[supernova]

With your #'s, it comes out to be 10.42 - 1. If you had a zero deck it would be 11.01 - 1.

You could raise the ratio to 12.1 - 1 just by milling the heads to 67 cc's and zero decking the block. You could get even more out of it by using a Cometic MLS gasket that is thinner. I run a .027 thick MLS Cometic.

[wikd69]

With your #'s, it comes out to be 10.42 - 1. If you had a zero deck it would be 11.01 - 1.

You could raise the ratio to 12.1 - 1 just by milling the heads to 67 cc's and zero decking the block. You could get even more out of it by using a Cometic MLS gasket that is thinner. I run a .027 thick MLS Cometic.

Wait, ya gotta compensate for the cam !!!! Chris, remember my big moment of revelation around my 'effective stroke' ? We need to know the intake valve close event timing, in degrees BTDC - that's what determines the actual, effective stroke, which when coupled with your combustion chamber size and head gasket thickness and overbore and head shaving and block decking and so forth, will let you determine your true static compression ratio.

See, this is what happens when you lets someone severely OCD go racing...

[ytnova]

I think he was just after the static compression ratio, in which case he would not need to know the cam timing.

[supernova]

Thank Harry!!! You keep my on my toes.
We might get to that later. Lets not overload his mind yet. He needs to get used to the 10.42 - 1 before we lower that #.

[434 nova]

Well now i am confused. lol My cam card says.

ex closes 23 atdc in opens 27 btdc

ex opens bbdc in closes 57 abdc

cam is 264-272 648-627 109 lobe sep

I want to put a supercharger on it maybe 10#s on pump gas and on race fuel pulley it to 15+ #s. Do you think it is possible with my compression.

[supernova]

Man I don't about the blower thing with that high of compression. We ran a 8-71 on a SBC with alki at 11-1 and 20 psi and got away with it but your talking about punp gas. You could get away with it on race gas but not pump gas. I though you going to run nitrous? Blowers are cool but you have to have the motor built right.
Hey Harry, your the resident blower guy chime in here and give us the low down.

[434 nova]

Yes, when i originally built the motor nitrous was the plan, but my buddy wants to get rid of his f2 so i can get a killer deal on one.