dynamic compression

[340duster]

Hey , good day all. I want to see if anybody has info on dynamic compression calculation for a 1967 Coronet with a 383 that I am building . it is a .030 overbore with KB 400 series pop up pistons (6cc) I have both the .020 and .040 head gaskets (not sure which ones to use until I get the engine and heads back from the machine shop and cc the heads and check deck height . I am shooting for 400 hp and have a lunati vodoo cam #60302 with about .475 int lift and .495 exh lift , I did a mild gasket match and bowl port , have an eddie perf rpm intake and new holley carb . stock resized rods and forged crank . billet adjustable timing set . as well as magnum hi per cast manifolds , from the static compression calculators I have used , messing with a few variables I am not sure about until I do the final measuring ,I get any where from 9.5 to 10.8 to 1 . the heads are 516 closed chambers . I am looking to run premium pump gas , which is likely 91 a best unless I get an ethanol blend that would be about 93 octane . the car has a shift kitted 727 with a 2500 stall conv. and 323 gear ratio .also does any one have solid info on the cc of the 516 heads I have been searching all over and get anywhere from 80cc to 88cc. (I guess I will know for sure when I cc them after the machine work. thanks in advance .

 

[Meep-Meep]

The 516 heads should be right at 80 cc's. The open chambers are 86. I can tell you that 10:1 CR and 190 PSI won't work with pump 91 but with that cam you will probably bleed off some pressure due to the later intake closing point so you might be OK.

The right way to do this is to select the static compression based on octane rather than letting the cam band-aid the issue by bleeding off the too high compression engine.

 

[340duster]

thanks again , I still await my parts from the machine shop . once I do all the final measurements I will get back to you on the final compression ratio .