In the middle of my 318 build and am wondering should I deck the block or mill down the heads, to raise compression. I roughly am calculating a 8.85 to 1 CR, showing my figures below. This will be an all street cruiser/no racing, just for fun car, want to run pump gas. Here are some stats: 71 ebody, auto 42rh built up, 318 at .30 over (original block), sidewinder alum heads (waiting to order), .028 compress. thickness head gaskets, H814CP30 Speed Pro hypuerectic pistons, Lunati retro roller hyd. cam 270/279 .515/.530 lift, Thermoquad '73 4 brl carb., no intake selected yet but alum., prob. use 1 5/8 headers.

Here is my calculations for CR using Diamond Pistons website, I did an educated guess on top of piston ring to top of block of 7/16":

Enter the number of cylinders of your engine 8
Bore 3.94
Stroke 3.31
Rod Length 6.123
Gasket Bore 4.14
Comp. Gasket .028
Block Deck Height 9.60
Top Ring Down .4375
Chamber Volume CC 63
Dome/Dish Volume 0
Piston to Deck .067

dimension results:

Total Volume 745.57
Cylinder Volume 661.34
Clearance Volume 84.23
Gasket Volume 6.17
Top Ring Volume 1.68
Deck Volume 13.38
Piston Top Land 3.902
1/2 Stroke 1.655
Compression Ht. 1.755
Cubic Inches 322.85

For the given dimensions, your compression ratio = 8.85


Do you see any errors in my calculations? With these calculations, would recommend to deck the block, mill the heads, both, or neither?

Would you recommend 1.5 or 1.6 rockers?

Thanks!