Thread: 383 400 rwhp build

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Appreciate that rodger. Never put that into perspective.... What is a good scr to run 87?

Originally Posted by jamesnelizabeth

Appreciate that rodger. Never put that into perspective.... What is a good scr to run 87?

I'm not smart enough to give you a hard & fast answer, as there are just too many variables involved - cam timing, operating temperature and head material to mention a few (aluminum heads help by dissipating heat faster). I'm running 10.3:1 and I drive 15 miles to get zero ethanol 91 octane most of the time, and buy premium on the road. If I were doing it over I would probably dial it back to around 9.5 to one and try to run 87 or mid-range 89 octane. One problem is that ethanol blends start breaking down after about two weeks in the tank, and once they do their phase separation they lose six to seven percent on the octane scale - 91 becomes more like 85, and there's no way to know it other than the ping. This is more of a problem for the occasionally driven "play car" than a driver. Others may be able to give a more technically sound answer on the best way to decide your static compression target.