ummmmm no. PSI and cr/CR/Scr are not directly related in that way, because the intake Closing angle is governing when the pressure building begins.
You can have an 11/1 Scr engine, that will build 20 different pressures with just one cam, at different altitudes and different installs. So talking Scr is somewhat irrelevant.
The pressure is what you want to talk about. Because the same engine operating at different pressures will have different operating characteristics.
Once the operating pressure is in the zone, it is very difficult to pinpoint a "perfect" pressure.
The "zone" is somewhat ethereal, in that it's hard to pinpoint, moves around, is different for every engine and different for every combo.
#1, max pressure is only possible when the throttle is at WOT.
#2, the pressure is only maxed over a narrow operating window
#3, the maximum changes with the amount and density of the airflow.
#4, the lowest rpm that max can occur is governed mostly by the cam. as is the highest point., but
#5 the highest point of max pressure can be stretched higher by the heads, the headers and even, the exhaust.
#6, there comes an rpm band, where there is just not enough time for the atmosphere to find it's way into the chamber as it once did, and pressure begins to fade into oblivion.
#7, What streeter drives around at WOT, at 3800rpm, all the time? Nobody does that. So in all likelyhood, something like 95% of a street engines life is gonna be NOT at max pressure.So there is no "best" pressure.
But in the same engine, you can find better and worse comparative pressures, like 160 is better than 150, is better than 140 and so on, because the more pressure you have, the less throttle you will need under every operating condition, except of course at WOT,lol.
Or;
There is NOTHING you can do for a 110psi 318. It's a lazy lazy dog and will stay a dog no matter what you bolt onto it, short of a supercharger.
An Iron open-chambered 360 will not accept much more than 160 psi, before it will start to detonate itself to death, on pumpgas, at WOT, sometimes less than WOT.
So we come to a zone that is pretty safe; say 150 to 158psi, and it is desirable that more is better.
But this number changes with every cam you put into it, and every different installed Ica, and at different altitudes.
So you have to pick the cam, or at least ballpark the Ica FIRST, so you can better target the pressure.
If you goof, and the pressure is too low, all is not lost; the bottom end just gets soft, which you can mostly compensate for with stall, and rear gear. But if the pressure is too high, for pump gas, then yur screwed, and will have to make some changes, usually major ones.
In my engine, I have kept the cranking cylinder pressure very close to 180 psi with all three cams I have installed into it, by changing the total chamber volume in each case, in compensation for the changing Ica which varied from 74* to 61* to 66* . The Scr ranged from 11.3 to 10.7 to 10.95. I did this by changing gaskets and by shaving the tops of the decks. For aluminum closed-chamber tight-Q heads 180psi is a walk in the park, as witnessed by the 87E10 it burns 100% of the time, with full timing.
And 180psi is awesome; waaaaaaay better than 150 to 158,lol.
Hope this helps
