I live in utah 4,400 ft. above sea level. I am wondering how much elevation will effect the maximum compression from a motor? Can I get away with higher compression on pump gas? 12:1 CR LT1 too much?

 

Remember pump gas there isn't like pump gas here at sea level (93 octane).
You guys have 91, or at least that is what they had in salt lake city.
With fuel injection, Al heads, and 91 octaine at that elevation I would not be affraid of 11:1.

 

I have seen people around here running 11.5 no problem. When I say here I mean SLC baby.

 

Yes you can put more compression in it, everything is about cylinder pressures and you don't have as much density at the same air temps.

Bret

 

At higher altitudes you can run more compression with the same octane fuel as lower altitudes. High altitude also needs less jetting and can use more timing.

That's all assuming the engine is NA. There's just less air to burn so the engine makes less HP.

It's like asking what temperature does water boil at. At sea level it boils at 212* but at higher altitudes it boils at a lower temperature. It all has to do with absolute pressure. Less pressure in the cylinders means you can increase the compression ratio without having detonation with lower octane fuels.