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Originally Posted by Cab_Burge
I use a thin blade screw driver to rock all the pistons over(stick it between the piston top above the ringlands) so the piston will be forced up against the outside cylinder wall and I measure the inside edge(cam side) of the piston deck and record it, I do the other side with the screw driver and measure the outside edge and write it down. You can average those or use both measurements for figuring the compression ratio on one of the online comp. ratio web sites like United Machine or Wallace scope Don't be surprised to see between .010 to .004 differences on deck heights depending on the piston to wall clearances shruggy
I have found that the crankshaft rod journal indexing, the length of the rods center to center and the piston wrist pin locations all influence the piston deck heights at TDC work I've also seen stock Mopar blocks be tapered from front to rear and vary on both sides, Stock production machining tolerances where not set to meet blue print specs work puke
Have you check the size of the combustion chambers, all eight of them, yet? If not do that now if you want to find to how much the compression ratio varies on your motor scope up wrench up whistling grin


Thanks for the answer! I have understood that vary in deck height is not unusuall on these engine blocks. The engine is assembled and camshaft broken in, i have around 400 trouble free miles on it so far and it runs great, have huge torque, i havent beat it yet with more than about 4500 rpm, it really makes my 300 -64 on over 4000 lbs to move, no detonation problems on pump gas, it running great, i know where i be around in compression ratio, it be from 9,97:1 to 10,3:1 in static and dynamic from 8 to 8,05:1 so it should work well on pump gas and it do. The accurate ratio depends on how accurate my measurements of how far the piston in the bore is but for sure they all eight is more than the theoretical .025", that i can see with only eye on the picture and i meassure them all 8 to around .040", it also depends on if the gasket bore is 4,38 or 4,50, the edelbrock e-street i have just trust they are 84cc

Last edited by Mopar493; 12/17/19 03:20 PM.