Setting deck height for 9:1 compression Options

[Chad911sc]

I have my short block built and I’m ready to set my deck height. It’s 96mm bore with stock 71mm factory crank. This is a 2.0 2056 build. I have a Web 86a cam calling for approx 9:1 compression. I have 60cc heads with 3cc valve reliefs on my flat top pistons. If I plug all this into the calculator, I get 8.3:1 for my compression ratio if I set the deck height to .040 inch
After I set up the piston on the rod and bolt down the cylinder to the block, I get .053 inch from the piston to the top of the cylinder.
My question is, what is the best way to proceed to get the 9:1 ratio with at least .040 inch total deck height.
I am thinking that if I take off 6 total cc’s from the head, that will leave me with 54cc heads with the 3cc valve pocket = total 57cc’s. Bringing me now to the correct 9:1 compression ratio with the .040 inch deck height.

If I am in the right ballpark, this means I need to have my heads fly cut….correct??
If this is correct, how do I go about calculating how many thousands of an inch do I need to have removed by the machine shop to remove 6cc from the head?

I obviously will need to remove at least .013 inch total deck height get to my .040 goal, and that’s with no shims or head gaskets being used.

Thanks for your time, Chad

[Jack Standz]

I, personally, don't believe EVERYTHING Jake Raby says. I'd guess at times; he's kept some data "close to his chest" and allowed misinformation to flourish.

The whole Raby "proprietary cam shaft profiles" is sort of BS as well. Adding 20+ degrees to both intake and exhaust and THEN spreading the LSA to 112-114 degrees was a GM trick first. This ALONE got rid of the EGR valve in the second gen small block (LS1) in the late 90s...

EDIT: In your case I'd talk with the machine shop. I'd say "I think I'm pretty close to flat, I want you to deck the registers TO THE MAIN BEARNG BORE and take off at least .XXX. If that doesn't clean it up, go further until it does and measure how much you had to remove in total."

That is the best way to skin that cat IMO.

Yes, don't believe everything Raby says either. But, when someone has built and machined so many type iv cases compared to other of us mortals, I think his comments and rules of thumb are not to be ignored.

Yes, agreed on the proprietary camshafts. For example, one of his camshafts seems to be very close to Webcam 163/86b. Among other things, he added duration to the exhaust to crutch a weakness of the type iv exhaust ports.

And to Chad911sc (BTW 911sc has been my favorite Porsche for a long time), no matter what they tell you, carefully measure everthing yourself. And my apologies if I came off a little gruff this morning. I'm still pulling for you to end up with the motor you wanted to build at the end of the project. And that it lasts for a very long time.