I have a 68 Charger with a 440. The motor is an 11:1 iron head motor with tight quench and runs fine on pump gas. I recently moved from PA to CO. Track altitude back in PA was around 1200'. I now live at 7400' and the track at Bandimere is around 5500' I think. I'm going to re-do my motor and am thinking a new rotating assy and alum heads. Would like to know from folks living at high altitudes like this what is the practical highest compression I can get away with with a tight quench motor at these altitudes given the highest octane pump gas available around here is only 91 octane. I know the guys who race Pikes Peak run some really high compression due to the thin air and the low barametric pressure at high altitude. Any guys out there have experience with this?

 

Bump the compression ratio to 13.0 /1 and run E-85.

 

I was told how they solved it but for the life if me i cant remember.
Timing &
A/F ratio