IMM Engines 408 build

yellow rose said
Where did you find this calculator? I don't see it on the Wallace site.

Here: Wallace Racing: Dynamic Compression Ratio Calculator

mullinax95 said
The duration is more on the new cam but the LSA went from 112 to 108... this might have something to do with it. Old duration was 226 the new is 230... not that much difference but....

It actually calculates both... here is a example .. the V/P is at the bottom

Static compression ratio of 9.7:1.
Effective stroke is 3.15 inches.
Your dynamic compression ratio is 7.85:1 .
Your dynamic cranking pressure is 151.86 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 7.69 :1.
V/P (Volume to Pressure Index) is 146

OK, I just have zoned out on the V/P number being there! (I don't pay much attention to it.)

I have run your 2 cams and still don't see nearly as much of a difference in DCR or V/P as you show in post #92 .... at most, I find the change is from 140 to 147 due to the LSA change alone. HOWEVER, I am guessing that both have similar ramps from .050" to advertised but that is just an assumption... I don't have any advertised numbers to know for sure and the old cam may be much longer on advertised; that moves out the intake closing a lot more than I am assuming.

BTW, I use a different calculator to get to DCR