Help me with some math Please

You are correct about needing to know head gasket thickness, and what they are referring to is "crushed" thickness........for a standard head gasket in a rebuilders gasket set, you will need to dig into the manufactures catalog, though truth be told, I'd look some place else for a gasket, not that they are bad, they are good gaskets for a standard rebuild, and it sound like that's not quite what you are doing. Fel=Pro, Victor Reinz, Mr. Gasket, Cometic, virtually a dozen manufactures have a gasket you are looking for, generally something thin......call their tech lines, talk to them, tell them what you are doing, it's their job.

You didn't say what year your 440 is....not that it makes a whole lot of difference, just nice to know where you're starting from. At around 4.325 inches bore diameter, you're around .005 inch O/S, standard bore is listed a 4.32 inches.....You might want to consider boring over size.

The following is an illustrative example:

From the Icon piston on line catalog, piston number IC822 has a compression height of 2.067 inches, rod length is 6.768 inches, one half stroke is 1.875 inches, add them all up and you get 10.710 inches, factory blue print deck height spec is 10.725 inches, that puts the piston down in the hole .015 inches at top dead center. Also from the Icon catalog, piston eye brow(valve relief) volume is 4.5 cc.

Compression ratio is total volume of cylinder with piston at bottom dead center divided by total volume of cylinder with piston at top dead center.

Cylinder volume is: pi times radius squared times height
pi: 3.14
r squared: (2.16 times 2.16)
height: 3.75
all of this equals 54.96 cubic inches, multiply by 16.39 and it equals 900.7 cc's

Head volume: already measured and averaged at 85cc's
Gasket volume ( Fel-Pro, from Summit racing catalog): 9.762 cc's
Piston volume: Icon catalog, 4.5 cc's
Deck volume: pi times radius squared times height
This is volume above piston when it is at top dead center, your height is how far the piston is down in the hole, don't forget to convert to cc's.

Now add: cylinder volume, plus head volume, plus gasket volume, plus piston volume, plus deck volume. Now divide what you just added by: Head volume, plus gasket volume, plus piston volume, plus deck volume.

The number you get is your compression ratio.

It's not that hard to do, I figured it out and if I had a dollar for every "F" and "D" I got in math in school, I'd have never had to go to work.

Hope this helps