Compression calculations

[NC Engine Builder]

I know there's alot of members on here way sharper than me, so maybe one of you can help me out with some math. I have a stock stroke 340, .030 over which is 4.070 bore, trying to figure the compression ratio. We have a 71 cc chamber, a .039 compressed gasket, a .016 positive deck piston which has a dome. The dome measures 11 cc, and the valve reliefs measure 9cc, can anyone help figure this? Thanks in advance!

 

[Max1196]

10.52 with a few assumptions. Gasket bore diameter?.

 

[NC Engine Builder]

I believe the gaskets have a 4.180 bore

 

[Max1196]

10.43 to 1, unless I forgot something!

 

[j par]

I know my Pistons are flat tops with reliefs and 4.040 bore and about 5 cc's above deck. 71cc open chamber head and the manufacturer calculate 11. 3 to 1.

 

[khuebner250]

I know there's alot of members on here way sharper than me, so maybe one of you can help me out with some math. I have a stock stroke 340, .030 over which is 4.070 bore, trying to figure the compression ratio. We have a 71 cc chamber, a .039 compressed gasket, a .016 positive deck piston which has a dome. The dome measures 11 cc, and the valve reliefs measure 9cc, can anyone help figure this? Thanks in advance!

Do you know top ring down? Deck height?

 

[RustyRatRod]

10.494:1 You have to add those 9cc's of valve reliefs to the chamber volume. Once you do that, it's pretty accurate.

 

[Dartfreak75]

Engine's Compression Ratio
I use that one it's pretty easy to use! And pretty accurate.

 

[Killer6]

11.1:1,.............

 

[JBurch]

I took my shoes and socks off so I could use my toes for counting and came up with 10.49 to 1

 

[j par]

10.494:1 You have to add those 9cc's of valve reliefs to the chamber volume. Once you do that, it's pretty accurate.

I took my shoes and socks off so I could use my toes for counting and came up with 10.49 to 1

I knew triple-r would be way off!