Compression Ratio

Scott714

Scott714

Club Member
Been looking for a formula or answer. If you have a 10 to 1 motor with a 52 cc head and change to a 58 cc head what will it change the compression ratio to ?
 
Bore x (Pi x R squared) X stroke = Swept volume (V1) x 16.4 converts cubic inches to CC.
Add head volume + gasket volume (in CC's) = V2
Divide V2 by the total of V1 + V2. Answer is your static compression ratio.

Somebody check me on this! It took me longer to figure out how to write it than it used to take me to DO it!
 
here a site I found and heres the formulas they had on there

http://www.rbracing-rsr.com/compstaticcalc.html

If you want to take the formulas with you and put them in your tool box, here they are. 16.387 is a number than converts cubic inches to cc's.

Displacement = (Bore ÷ 2)2 x 3.14 x Stroke x 16.387
Head Gasket space = (Bore ÷ 2)2 x 3.14 x Gasket thickness x 16.387064
Deck Height space = (Bore ÷ 2)2 x 3.14 x Deck Height x 16.387064
Compressed Volume = Head Gasket space + Deck Height space +
Piston Top volume + Combustion chamber volume
Uncompressed Volume = Compressed Volume + Displacement
Compression Ratio = Uncompressed volume ÷ Compressed volume
 
I'm feeling real stupid right now.
I forgot to mention the fact that my formular involves having the ACTUAL measurements for the dome (or dish) volume.
Use forcefed's numbers. I'm just shutting up now...
 
On a 350 cube engine, you are going to lose .5. Check out piston kits and how they vary with different chamber volumes. Should be very close.
 
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