Anyone use Avgas 100 LL in place of racing fuel?

Hey Guys,

Has anyone ever used Avgas 100 LL in place of racing fuel? How did it work for you? Any potential dangers in using it?

Thanks!

I personally never used it but a friend of mine did. Carb & timing adjustments. This was in a stock 440 street car that wasn’t driven all the time. Don’t want what the internals looked like. Do a google search on av gas in a car engine and make your own conclusion.

Probably at least 10,000 people.

I've been using it in my street driven 10.5 compression 68 GTX since I finished the restoration in 2015 and I use it in my 11.0 compression 360 Magnum 67 Dart bracket car, never had an issue, helps that I live next to a small airport.

How much is AV gas these days??

I stop using Av Gas, not 100LL, in my race cars back in the mid 1970s after seeing the pitting the valve seats and valves it caused in high RPM motors, above 4000 RPM
I have used some 100 LL in some other Hi Po street cars since then due to it having shelf life of 18 months, it has a noticeable distinct smell that some law enforcement officers can notice, it has a $10,000.00 Federal fine on using it on the street due to the lead content, if they want to write you up for that
I owned and flew a small airplane for a little over 15 yrs, spent around 900 hours in flying it with using 100 LL only fuel in it.
Before leaded additives where outlaw for street gasoline there was three different blends of Aviation gasoline in the 1970s, 85/100, 100/115 and 115/145 which later became 115/130 octane. I use the 100/115 in my race cars back then

Long, long ago- like 40 years ago - some of us SoCal guys ran either 100 or 110 IIRC AvGas..
We had an "in" at the Van Nuys Airport.
Those were 12.0-12.8:1 street racing deals.
Don't recall much about any long-term effects.
Probably a different blend nowadays, anyway.

http://www.100ll.com/

Previous thread on avgas. The topic comes up a couple of times a year.

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/2560934/1.html

I've not used it in years, and over here, it's just easier to buy some of the more basic race fuels.
I don't really recall there being any real difference in power, compared to the 100 octane race fuel I used instead of the AVgas. I recall the AVgas likeing more ignition timing.

Thanks, I did a search first and didn't see anything.

I know a few guys that run it and it seems to work okay. My sister runs it in her car and hasn't had any issues. I tried it 2 years ago and made a whooping 2 passes with it. My engine is 11:1 and I was doing a mixture of pump/race gas before so I tried it. Had to readjust the floats. I drained out the tank, filled with AV gas. On the 1st pass the car stumbled. On the 2nd pass the car kept wanting to shut off. I was able to get the car back to the pits and realized the fuel pump was acting up until it finally wouldn't run at all. I don't think the AV gas had anything to do with it since the Holley Black pump was about 12 years old, but I ended up draining the tank, going back to my pump/race gas combo and putting a new fuel pump on the car. Used the rest of the AV gas in the lawn mower. At that time AV gas was like $2.50 a gal.

I started having Sunoco 100 unleaded delivered in the 54 gallon drum. I switched my cars over to F.I., so I can't use leaded anymore. Seems the Sunoco 100 works well in my 10.8:1 440 stroker, 87 Buick GN and my 11:1 stroker small block.

Know many people that have used it for years never a problem. Some big blocks with high compression some boosted LS engines

I cannot give you the details or the science behind it but I have heard folks say that the Avgas is blended for high altitude use and that makes it less than optimum for race cars.

I had a friend that was an engineer that said Avgas burned too "dry". I don't really know what he meant.

well be prepared to clean your plugs and dont idle too long. Tops of pistons will get lead deposits but it runs good. 100 Low lead is not really low lead. I would blend it with 91...and I clean a lot of spark plugs at work because we have 50 airplanes and about half run low lead...Tim

two things about todays 100 LL, it is a lot thinner, less specific gravity, than todays pump gas or todays race gas. Maybe he was referring to this As far as altitude and the design of Av Gas back in the day when commercial pressurized airliners ran Av gas they did tend to fly a little higher on the altitude than your normal non turbo charged or super charge piston engine airplanes fly normally for several reasons.
Most piston driven non pressurized airplanes used today fly at or under 12,500 ft. above sea level for several reasons, one of them being the pilot is required to use oxygen above 12,500 if they are above that altitude for more than 20 minutes.
I flew a friend and his grown 30 yr old Son to Denver and back from SO CA around 20 yrs ago, I had a five place oxygen system in the airplane with new canula for breathing at or above 12,500 ft. I had to go above 12,500 ft. going and coming back and they didn't want to use them, they both went to sleep and where groggy with a head ache on the return trip. I decided to fly direct from Denver to the Grand Canyon airport on the return trip to save time and fuel as we where able to depart the small airport in south Denver before 9:30 AM. I flew at 16,500 Ft for around 1 hour before descending down to 8,500 near Gallup N.M. so they wouldn't get oxygen starvation and suffer for the rest of the day. That didn't work as the damage had already been done
I had to lean the mixture out mechanically from the cockpit with the leaning mixture knob anytime I flew 3,000 above sea level to avoid fouling the spark plugs I accidently foul one spark plug on my second flight after buying he airplane, only once That is not a good feeling when you loose the use of one cylinder on a six cylinder engine and your 3000 + Ft above the ground

I always like hearing this, its for high altitude. Pretty sure all airplanes take off from the ground and also pretty sure taking off takes more power than actually flying. I use it, and love it. 12 to 1. The car doesnt get driven much, so when the fuel evaporates, it doesnt leave any "goo" in the carbs. You have to jet up a little, not much, but some to make it run right. Carry on. It was 4.50 a gallon at the airport near me. LOL

then why does a place like denver, have a different formulation of fuel....

I use it in everything. My 12:1 Sport Bike, ATV's, Motocross Bike, 9:1 Magnum engines, 11:1 Gen 3, and all of the old cars. My fuel mileage is always better, they start quicker, and responsiveness at the pedal is noticible.

I blend it to pump regular because I always question how long premium sits around at gas stations. "Pump premium" is likely stale and dropped a few points from what is claimed on the sticker.

I'd rather the Haters keep hating on LL so there is more for Me.

Avgas 100 LL should be the same formula and chemical makeup no matter who makes it and where it is sold from
I've bought 100LL in Denver to get home from a trip there, no noticeable difference in the smell, price or performance on take off and climbing other than having to lean it out a lot more to get have 50 F degree rich of peak at WOT before take off
I was taught to always run the motor up to WOT and lean it out to peak EGT and then richen it up 25 to 50 F rich of peak at any airport above 3000 Ft. above sea level before take off, especially in the summer when the density altitude can get way above the local altitude

Thanks for all the info guys, this is great.

Go To yellow bullet website alot more info on guys running it and some dyno test etc

Too much misinformation going on. Too dry, made for high altitude... garbage. 100LL is rates 100 octane lean, 130 octane rich, compares roughly to a 110 race fuel. I have a 461" SB2.2 engine in my dragster at 15.5 to 1, I buy 55 gallons at a time and either use Turbo 108 Plus or Race gas concentrate, a bottle to 55 gallons, My best time with Q16 is 4.71 in the 1/8, with aviation fuel 4.74. $85 for 5 gallons of Q16, under $20 for aviation fuel. I don't suggest it for street use as it is illegal. E85 is a good choice for street if available.

jWe use it for dyno testing since it is easier to get than race fuel, is less expensive and it works better than a lot of other fuels. But that might not be the case for other folks. The dyno shop that I work with is located fairly close to a rural airport. Some airports will pump Av gas into containers and some wont. All depends on where you live and who you are. The dyno shop has trouble getting race fuel delivered and it is a long drive to buy it.

^^^THIS!!^^^

Back in the day, we could pull right up to the pumps and buy whatever we wanted, not anymore!

I've been to every airport in a 50 mile radius, and not one will sell to you unless you pull your plane up to the pump. Sure would like to know where you can buy it by the 55 gallon drum.