CR calculation, deck height/effective dome volume?

nm9stheham said
In your calculations, set DHV (deck height volume) = 0 cc, and SUBTRACT EHV = 2.2 cc Since you have positive net piston head volume sticking above deck, it will subtract from the chamber (CCV) + head gasket volume (HGV) when the piston is at the top of the stroke. (EDV? Does E stand for extra, external, extrapolated, extraterrestrial, egg-shaped? LOL)

Using my preferred calculator, and a .051" head gasket with a 4.17" hole (standard Felpro type), I am getting 10.6 SCR using your measured numbers for the piston 'dome'. So we are close.

OK on the decking.. that all makes sense. Are your 'X heads' the Indy-X types or Mopar X heads? If the latter, it looks they have been milled around .050-.060" to get to a 63-64 cc chamber volume.....yes? no? If they are Indy-X heads, then a close look needs to be taken at the head gasket thickness to insure adequate piston-to-head clearance.

Is there a reason to lower the SCR? What is the use for the engine? Street? Cruise? Pure drag race? Any info to share on the cam? Depending on this info, maybe the SCR needs to be kept as is...

EDV is the Effective Dome Volume, and as I understand it, normally becomes a negative number for the part of the piston that sticks above the deck. I used United Engine & Machine's on-line calculator with the numbers I generated, as well as .036 EDV and a valve relief of 7.5cc ( a figure I found for these pistons) and it produced 10.2+ and 10.3 respectively. I used a 4.180 x .040 gasket, at 8.9cc every time. My heads are the factory type, with Ferrea nail head valves and hardened seats installed. At first I thought I had confused my start amount in my burette (20 vs. 25), but after checking 3 more chambers, they are all within .3cc. I used the blueprint pictured when measuring the chambers, and they came out at .706 to.711. It looks like the heads have only had a cleanup? I haven't picked a cam yet, was thinking a pump gas friendly DCR (low 8's?) would play a big part in that. The motor will be for a street-only car (if I keep it).