Leaded vs. Unleaded?

[JJRJR]

At the risk of opening up a topic that has been beaten to death. . .

During my recent chassis dyno session, I was (always have) gotten a bit of run on when trying to shut the engine off when it's hot. The guys told me that other than making some mods to help with vapor lock and/or fuel being too hot (which it is) they suggested a higher octane fuel.

The best unleaded I can get in South Florida is 93. I'm running 10.5:1 CR and the timing is at 33 or 34 full advance I believe. The tuner said that's where we got our best overall performance BUT the octane was an issue.

OK, so can I use 100 low lead aviation fuel? Can I use a full leaded racing fuel at 108 octane? I want to stay away from octane boost additives as I've heard mixed reviews.

Any thoughts on the aviation fuel or leaded?

Thanks guys.

John

 

[69hemibeep]

With your aluminum heads you should be fine when you get the temp down. I have blended both with gas in the past without problems but 100% aviation is very dry and tough on certain rubber parts.

 

[Ranger]

I take it this engine is new?

 

[mac]

well 32 years ago when i was working on small airplanes, there was plenty of lead still in 100 LL avgas. i used to run it in my first road runner when i had to take care of the fuel trucks. would have to drain off about 10 gallons a day to make sure there wasn't any water and it went right into my car. when i was cleaning the lower spark plugs on airplane engines, i would have to chisel the lead deposits out. another thought is i used to run a lead additive to the 41 Buick so that may be an option to add to the 93 octane.