Hey guys- I'm considering trying some 100LL ('low lead') Avgas in one of my cars, currently fitted with a 650 Holley double pumper. It presently has #66 primary and #74 secondary jets with a 4.5 power valve and #28 squirters on both sides. As the engine is right now with 36 degrees total ignition advance it runs quite well; good plug color, no overheating, good throttle response, etc.. HOWEVER, I am considering using the car for track days and am looking for a cheaper alternative to racing gas, which 100LL would be at around $5/ gallon at our local airport. I would like to get a good starting point for carb jetting as I understand Avgas is lighter than pump gas and must therefore have a richer mixture....have any of y'all played with this stuff and arrived at a satisfactory mixture formula? Any and all advice would be greatly appreciated- thanks in advance.

 

When I ran a stock 11:1 CR 350-350 (excepting iron slant plug iron heads and a Torker intake) it ran PERFECTLY on 100LL.

100LL provides absolutely no detonation and no perculation.

I ran Edlebrock Varijection water injection to keep it from knocking for about 125,000 miles - the best auto gas would make the engine knock terribly.

If money is no object 100LL is clearly the sweet setup, but you have to watch for lead deposits if you don't run your engine hard enough. There are obviously environmental issues with leaded fuel (although no different than aircraft burning 100LL).

 

Better make sure you can get it - a) it's illegal for road use and b) many airports closely control taking a can up to the pumps.

What are you expecting from using 100LL? Higher octane <> more power; if you're able to run full advance with the engine and fuel you have, you're getting all the power the engine will make.

 

Private aviation air ports will carry that fuel and probably sell it to you but not directly into your tank. Take 5 gallon or more can or cans. I use a 15 gallon drum.

 

Just an FYI - this varies greatly state-to-state. The pumps are automated, but a) may have access control to be able to get to the pumps and b) may require an N-number (aircraft registration number) in order to buy the fuel. I'm a pilot - I run into this all the time.

Again - it's a waste for what you want it for...

 

It is made to run at 10,000+ feet is your track that high?

What do you hope to gain if your car runs fine on 91?

It is also a fact that additional octane is a waste and in fact if you put something like 20 points over what you need your motor will make less hp.

I get 110 leaded (car) from work and mix it about 30% with 91. So I end up with 97 or so.

 

Although it's been a long time, but I was able to get the fuel filled directly into my tank. I was amazed how quickly my '69's tank was filled!!!

 

It really depends on the FBO manager. If you go to some "podunk" field where Billy Bob is running the FBO, my bet is he won't care. If you go to a field with a "full up" FBO (the types corporate/mil guys use), you can forget it.

 

Before I go any further, thanks for all the replies guys. Initially the post was at 50+ views with no takers so I kind of gave up. Just to update, the day I wrote the post I finally did get over to my local municipal airport (the nearest gas station is one mile from my house, they sell 91 octane pump gas right now for 3.89/gal) which is two miles away and the kid at the counter happily opened the gate, let me drive the wife's Exploder onto the ramp right next to the truck and filled my jug with 100LL for the princely sum of $5.34/gallon. Of course no mention was made of what it was REALLY for. Went home, dumped it in, fattened the jetting up to 69 &78, cranked in 38 degrees of timing, and took it out in the heat of the day (95 degrees). Years ago I did a track day at Laguna Seca and put 100LL in the same car with no jet changes and the temperature shot up to 230 degree after about two hard laps- this time, no such problem, so I think I've maybe gotten it pretty close to what it wants. Again, the only reason I was doing this was that $5.34 leaded Avgas at around 115 octane makes a pretty attractive alternative to $8 or $9 108 octane VP. I've tried running pump gas at track days; the swill we get here in Ca just doesn't seem to work very well when you really want to lean on the motor for any kind of extended period, missing, sputtering, etc. when under heavy load. Again thanks for chiming in all-

Dave