Compression ratio help

[1973stang]

Bore X Bore X .7854 X stroke= Cylinder Volume V1

Bore X Bore X .7854 X Deck Height= Deck Clearance Volume V2

Bore X Bore X .7854 X Head Gasket Thickness= Gasket Opening Volume V3

Comustion Chamber Volume in CC's(cubic centimeters) To Convert CC's to Cubic inches, Multiply CC's by .06102 CC's X .06102= V4

(V1+V2+V3+V4)/(V2+V3+V4) = COMPRESSION RATIO




This is some info I found on another forum about compression ratios.

My build is on a 1973 351C with 2V 76.2cc .40 over bore, stock stroke.

I am using these pistons do I subtract 2 cc's from the cylinder head cc for the equation? Also should these pistons work and not hit the valves? Will I be able to run pump gas?

Any estiments on the compression I should be seeing?
The block and heads are stock deck heights

Keith Black/KB Pistons KB177-040 - Keith Black Hypereutectic Pistons - Overview - SummitRacing.com

 

[j_lutter31]

The link shows pistons with a dish. So you need to add 2ccs to the head volume. Hence the spec Piston Head Volume (cc) +2.00cc. Since they have a dish and not a dome, there is no chance of hitting valves.

 

[D.Hearne]

Piston to valve contact will also depend on the cam grind you're going to use. More so than those pistons. You will have no worries about running pump gas with those heads and dished pistons. Quite the opposite, you're going to have to choose wisely on a cam grind to avoid lowering the dynamic ratio with that combo.

 

[1973stang]

UPDATE

I plugged the info into a compression calculator and came up with roughly 9.8:1

The pistons barely have a dish, its just one valve relief if you take the time to look at the link.

And I was thinking a 268 comp cam or edelbrock performer. (going for mild performance.

 

[D.Hearne]

With a 9.8 to 1 ratio, the 268H is not the cam you'll want. Looking at premium fuel only with that combo. The 268H is designed for lower compression ratios.