I am running 9.4:1 compression and should be running 92-93 octane gas.
For my 1st fillup w/ the new engine I put in 105 AV gas, just incase something went wrong, the high octane would help out.

But now that all is fine, could such a high octane be hurting performance? This is what I was told; and that 92-93 would give better performance, ie: speed and acceleration.

too much octane doesn't help.... sometimes will make less HP

i run 87 in my HP500 all day with no problems... i like it that way

Too much octane definately hurts power. You are absolutly fine with 92-93 octane. FYI I ran 10.5:1 compression on 93 octane, alum heads on 632" motor with no problems at all.

Even if you're running iron heads you are fine....

Good news... and thanks for the confirmation.
Now I just gotta burn off another 25-30gals of this $4.09/gal stuff!
And get some 92-93 in there.

Mix 30 gallons of 87 octane with the 30 gallons of 105 and you'll get about 96 octane overall.

Octane rating is in no way correlated with engine power or efficiency. There is more potential energy in a gallon of diesel fuel than a gallon of gasoline, yet the diesel fuel has a much lower octane value. Bottom line is run what the engine can use.

brad is completely wrong in all aspects!! If your engine doesn't need 105 octane and can run on 89 then it will make more power because it is easier to light!! sense you are not making alot of cylinder pressure, by using the higher octane it is slowing down flame front travel and hence making less cylinder pressure (less horsepower). hope this helps. these rules don't apply to race fuel, because of the additives

fountain333 is right. Higher octane burns cooler because it has a higher flashpoint. Use higher octane when you NEED to to avoid detination from high compression and/or advanced timing. High octane is used to prevent detination, not promote hp.

Remember, heat makes hp, the less heat you make the less hp you make, period.

Like Griff said, I would mix the 105 with some 87.

While I have never treid AV fuels, I have heard that it doesn't run to burn well at sealevel. It is designed to be burned at altitude where the air is thinner. In any case, just make sure your fuel mixture is good when you switch to 93.

Read my post again..... I agree 100% High octane fuel does NOT make more power or efficiency by itself. High Octane burns slower thus allowing for higher compression engines to make more horsepower. I say again only use what the engine should burn for peak horsepower. As for diesel fuel having more energy, look it up.
Don't waste your money mixing race gas with 87. Running 93 with your compression ratio will be fine.