340 Static Compression Numbers and Test Procedure

340inabbody said
YR question regarding the compression if using the TRW L2322.

I am wondering if my compression is indeed 10.5-10.8:1. Wouldnt explain the static compression I measured. I verified my static cylinder compression measurements with another gauge type All are "high" `200.

Below I found this info on the TRW pistons (which are indeed .030) If my heads are 64CC (from below table) then si the information below correct indicating ~12.7 CR? Or am I missing something? This does jive with the 200PSI cylinder pressures I am measuring and also why I had seen detonation......... Not saying I have the right CAM as I think its a 4spd grind what every difference that might mean.....

NEW OLD STOCK

FORGED PISTONS

PART NUMBER

224-1836 PERFECT CIRCLE ( SAME AS L2322F TRW)

STANDARD BORE

340 CHRYSLER

DOME PISTON

63CC HEAD-- 13.09 TO 1

65CC HEAD-- 12.68 TO 1

68.4CC HEAD-- 12.05 TO 1

71CC HEAD-- 11.61 TO 1

The CR will only match these numbers if you use the thin gaskets (IIRC they are .021 or something...they were steel shim gaskets IIRC) and the deck of the piston is out of the hole a minimum of .017 and usually that's not out enough.

So the answer is it depends on the actual CC of the chamber, the thickness of the head gasket and the diameter of the bore in the gasket, and how far the piston comes out of the hole.

The two big things will be the head gasket and how far out the piston is. It's hard to find a machinist who desont have Chevy brain. You don't stick a Chevy piston out of the bore, so you can't do it on a Chrysler either. To do it right, the piston needs to be out of the hole. The thicker the gasket and the bigger the bore, the further out of the block the piston needs to be.