I'm going to pull the heads off soon (to replace valve springs) and wanted to know if I can calculate my static compression ration without knowing the piston manufacturer or specs (dome volume). On the first build the shop used Keith Black pistons and they don't stamp a part number on the top of the piston and I don't trust this shop because they have lied to me on several occasions. Any book or post that I have read required the information from the piston manufacturer. Thanks!

RN70,

The only way I can think to accomplish this is to:

1) Bring 1 piston up to TDC then measure the difference between the block deck height and the height of the piston (measured on the flat portion of the piston - not the dome if it has one). Use either a dial indicator or, if lacking one, you should be able to get pretty close with feeler gauges. Make sure you clean the deck surface of all gasket material first. The difference could reasonably be anywhere between zero and .040. Note that number.

2) Same piston; if it's not too covered with carbon coat the top of it with oil then press modeling clay on top of it - making sure to fill all voids EXCEPT the gap between the piston and the cylinder wall. Carefully remove the clay. All you are doing here is making a mold of the top of the piston. Once you have your mold, flip it over and use a syringe marked in CC's to fill the mold. Keep track of how many CC's it takes. Note that number.

Steps 1 and 2 will tell you how far down in the cylinder the piston is and how many CC's the piston dome is - two critical measurements.

3) You need to CC one of the cylinder heads' combustion chambers. You can use one of the CC'ing kits that summit sells or just get a piece of plexiglass, drill a hole in it, spread some greese around the perimiter of the chamber and press the P-glass onto it. Fill it through the hole. With both valves and a spark plug installed, use that syringe to fill it - again keeping track of how many CC's it takes. Note that number.

4) You'll need to know what the cylinder bore diameter is. If it's a standard bore 454 it's 4.250. If it's been bored, say, 30 over then it's 4.280.

5) Finally, you'll need to know what the compressed thickness of the head gasket you will be using is. If the gasket you remove is one of the blue Felpro jobs figure on something like .040 as a ballpark. You may even be able to find the PN stamped into the gasket then go look it up on Summit's site.

6) Gather all these numbers in your arms and run on over to Pat Kelly's DCR calculator and plug them in. It'll spit out the answer.

Dan

SS3964SP: Thanks for the info, I knew someone had a way of CC'ing the piston dome, I would have never come up with the idea of using clay. Thanks again.