LR1970
Well-Known Member
Hi, so in my research about compression ratios I have discovered all about Dynamic compression and cranking PSI. I am reading that for pump gas your dynamic compression should be around 8 to 1 and 165 psi cranking pressure for an iron headed big block. Does this sound right?
The camshaft I want to use in the build has a 74 ABDC. To get the 8 to 1 dynamic ratio I will need a 10.9 static ratio.
Is 10.9 static and 8 dynamic still ok for pump gas?
I plan to use Edelbrock 84cc RPM heads or 915 heads to get close to the 10.9 ratio.
Will advancing the cam change these ratios?
If I plan to install the camshaft 4 degrees advanced, should I be recalculating the static compression at 70 ABDC so then bringing the static compression down to 10.5 to 1.
Cam has same LSA and centerline.
Or am I just splitting hairs here?
I would like some real word opinions before I go to the machine shop for head cc milling.
The camshaft I want to use in the build has a 74 ABDC. To get the 8 to 1 dynamic ratio I will need a 10.9 static ratio.
Is 10.9 static and 8 dynamic still ok for pump gas?
I plan to use Edelbrock 84cc RPM heads or 915 heads to get close to the 10.9 ratio.
Will advancing the cam change these ratios?
If I plan to install the camshaft 4 degrees advanced, should I be recalculating the static compression at 70 ABDC so then bringing the static compression down to 10.5 to 1.
Cam has same LSA and centerline.
Or am I just splitting hairs here?
I would like some real word opinions before I go to the machine shop for head cc milling.
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