Formula for compression?

[punisher72]

Hey guys,is there a formula to work out the compression ratio? My 440 has the 84cc eddy heads and I have standard head gaskets. The piston is 30 thou lager than standard and is 17 thou below deck. If my compression is too low I'm thinking of buying 30 thou ova pistonsthat come up above the deck to bump it up and still run unleaded. What do you think? Cheers for any help.

[punisher72]

I tried to fill this calc out with a few guesses?

Enter Bore/Stroke Designation Type
1 = Inches 2 = Millimeters                                                                   1
Enter Cylinder Bore Size                                                                       4.380
Enter Piston Stroke Length                                                                  4.375   
Enter Head Gasket Bore Diameter                                                          4.380 
Enter Compressed Head Gasket Thickness                                               0.035   
Enter Combustion Chamber Volume In CCs                                               84cc
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-')         0 
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') :                  0.017
         


     
Calculated Engine Compression Ratio                                                      10.56.1



Does this look anything like what it should be? The bore is 0.030 over,standard head gaskets and the flat top pistons have small valve reliefs. The block was cast in 1977.

[the_engineers]

Seems pretty close.

[Changin Gears]

I would go ahead a put -3 or -4 in dome volume for the valve reliefs. 

[ireland383]

I think the standard Felpro gasket is 0.039.