We have all heard of people trying to get the most out of their a12. I'm just wondering what people have heard of or done themselves as far as compression in each cylinder. I Have heard upto 250psi in each cylinder, what's the highest you've heard. Obviously people are going to ask what modifications he had, so mild can 60 up flat tops a pretty standard carby and a bit of head work. My real question is what can they handle!

They can handle more than 14:1 compression.

This is an A12 piston sold by Datsun Competition

250psi , sounds like an engine built for economy. High compression ratio but with a mild cam? Or a race engine where the rules don't allow a change in cam?

I was wondering the same thing, because high-compression, high-rpm engines have lower psi during a test. Low-rpm engines have higher psi

High Compression Ratio does not equal high cranking PSI

A restricted engine, say a race engine that has to run the standard carb, are often built to have high compression. They can run a high manifold vacuum (maybe 6" at WOT) effectively reducing the compression when under full load. Cam timing also has a big bearing on cranking pressure.

At 250psi it would probably be an alcohol engine or a restricted engine?

Help is out GG, what sort of engine is it? My A12 only cranks 110psi. Flat tops with a big cam.