Hi Paul,

I did know about the different methods because I spend a bit of time in the US. The effective difference between what we in Australia use (RON) and what the US uses (RON + MON)/2 is about 5 points. We're higher. My engine is currently tuned to get away with running on 91 (in Australia) which means I could get away with about 86, at lower altitudes, in the US.

In reality I use 98 here and it certainly feels better. I'm currently running 9.3:1 static compression but plan to raise it to 10.5. Then I'll certainly need to run 98 (or 93 in the US). Plus carry some octane booster. I've a got a programmable 123 distributor in the car, so I can set one of the ignition curves to retard the timing a bit if we get pinging. It's switchable on the fly.

As a side note, having seen the costs of shipping the car to the US - for some reason significantly higher than shipping it back - I'm thinking about buying a car in the US to do the event. I've always wanted a 70-72 Corvette... I've got garaging in Colorado so it actually is a possibility.

Regards
--
JohnH, Sydney, Australia