Piston question
What you really can't afford is a do-over. And that is what we are here for; in an effort to help you do it right the first time.
I remember in 1998 when I was planning my engine. Every big-name engine-builder I contacted recommended 9.5Scr as the max for my combo. I had already decided to use alloy heads, and 9.5 was still the recommended max.
But I was pretty sure with alloys I could go higher. So I figured out that the Ica was a huge player, and that it wasn't Scr that was the problem, cuz you know, racers were running 12/1 and more.
So I set mine up at 11.3/1 with a Dc 292/292/108 cam; and set about to tune that. And it worked. The key was the alloy heads, that let me run 180psi and more. That engine ran gangbusters strong.
It didn't take me long to figure out that pressure was king, but detonation was the achilles heal.
So you can't run 180psi with iron heads on the street. IDK if you can run 180 at all on pumpgas, but I would guess no.
IDK what exactly you can run.
But I can repeat what I have learned here on FABO. which I compiled and showed in a previous post.
And namely;
165psi with a tight-Q is about the limit on 91 gas.
For you, I would suggest 160 with tight-Q, to run 89 gas, giving you a degree of safety if you screw up on the tune.Or, lacking a tight-Q, I would suggest 155psi.
To achieve this, you need to know what cam you will be running, and that will be governed mostly by the application, which includes the rear gears and stall. And by the elevation at which this engine will be operated at.
If your budget is tight now, wait until you have to change both the gears and the stall because your pressure ends up too high! Or, if you install a way-too-big cam, and it drinks gas like a camel drinks water in the desert.
I was fortunate in that I had a lifetime of parts accumulated, to match my engine to the application..... but before the first summer was done, that 292 cam was already out and sold. It mightabin a great race cam, but it did not suit my application.
IMO;Application is everything.
