[KevinDush]

Although AV gas has been mentioned numerous times on the board, I think it should have its own topic. Lets hear some opinions and of people's actual experience, and make sure to note your CR and probably camshaft specs as well. How about mixing and things like that? Does it actually work? What kind of octane are we talking, obviously its nice because it is cheaper but are there any negative side effects? I don't know much about it so I'm waiting to hear from you guys.

Later,
Kevin F. Dush
kevin@Fizziwigs.com

[KevinDush]

Although AV gas has been mentioned numerous times on the board, I think it should have its own topic. Lets hear some opinions and of people's actual experience, and make sure to note your CR and probably camshaft specs as well. How about mixing and things like that? Does it actually work? What kind of octane are we talking, obviously its nice because it is cheaper but are there any negative side effects? I don't know much about it so I'm waiting to hear from you guys.

Later,
Kevin F. Dush
kevin@Fizziwigs.com

[TinInjun]

A little history about AvGas.
Back in the old days, there was three most common grades. 80/87(red), 100/130(green), and 115/145(purple). These were the most popular.
The first number indicated the octane of the fuel on a lean mixture and the second number was the octane on a rich mixture. (aircraft have manually controlled mixtures)
Well, back a few years (over twenty) the government stuck their nose in the tent and decided that there was too much lead in AvGas. Thus behold we now have 100LL(blue), the "LL" stands for low lead. Its was just given a single octane rating, unlike those in the past that had the dual octane rating. Fuel manufacturers took out some of the lead and added benzene(and some other stuff) because of its anti-knock qualities.
The only problem you may encounter running 100LL is hard starting in very cold temperatures. It will not rot out your rubber fuel lines like fuel that has alcohol mixed with it. It will not burn your valves either, like I have heard from so many misinformed people. It smells different when it burns and because it has lead in it, it will destroy your catalitic converter(if you have one). It is also illegal to run on the street because it is not taxed like automotive fuel.(like anyone would ever get caught by the tax man) It is illegal to be pumped directly into a car, so unless you have a friend that pumps fuel at the airport, you better bring a bunch of 5 gallon jerry cans to fill up.
The average comp ratio on aircraft engines is 8 to 1, and I have never seen an aircraft engine that has been damaged by detonation when running 100LL(even turbo motors that run 42" of manifold press at max power)
I have run 11 to 1 Pontiacs on AvGas and not heard a bit of detonation or seen any damage when the motor was torn down.
Wow, I haven't written that much since I got out of school [img]/infopop/emoticons/icon_smile.gif[/img]
Just my .02 cents

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"Run wild with an Indian, not with the crowd in a Chevy"

[Michael Farich]

Back in '85 I ran 100LL in an LS7 454 with an LS6 cam. Holley 800DP set up by an experienced tuner who said the 100LL would be fine with his carb tuning. It did smell funny when you stopped and the wind blew the exhaust past the front of the car. Never had any problems with that motor and it was 12.2 CR. Drove it 1500 miles street and strip.

[Bob Dillon]

Concur with Tinny. I've run Avgas (100LL) in a 10.75:1 race car with a short cam and the engine never showed any signs of detonation, even with lots of ignition lead.
I DO note, however, that several N20
manufacturers do NOT recommend Avgas. I don't know why, but they obviously tested their products and know best.
Remember, with the addition of TEL to gasoline, the first small amount adds a lot of octane, and adding more also raises octane, but on a declining curve.
I go to the air races in Reno all the time, and the unlimited class racers (usually P-51 mustangs and F-4U corsairs or F-8 Bearcats) still use 115/145-with 10% nitro!
So, it's available some places but my suspicion would be that it's at least as expensive as race gas.
At my local airport 100LL is now going for $1.75 plus sales tax, and is now cheaper than super unleaded in my area! Tinny is right, get a couple of 5 gallon PLASTIC fuel jugs from Summit and use those. Most fuel facilities are automated now and take credit cards. They also require an aircraft tail number to pump. BUT, you're at an airport, look around and the solution will be obvious.
Be SURE to use the ground strap to ground the fuel jug during pumping.
T

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Jesus is coming again. Look
busy!

[Tim Corcoran]

I have run 100LL in my 65 LeMans 12:1 455 with 16 heads. Solid cam 255/263 @.050 and 597/603 lift on a 108 LSA installed 3 degrees retarded. I have heard that you need to richen up the mixture a bit when using thr av gas. I didn't experiment with re-jetting but I did my best time ever with a 50/50 mix of 100LL and VP 112 race gas (11.23 @119.75). I have a friend that has been running 100LL in his street driven 70 Judge for years. He also races it at the track. He claims 11.5 to 12.0 compression. He has 30,000 plus street miles on the motor and several hundred 1/4 mile passes on the same engine (455) with out removing the heads. I don't know his cam specs but it is a four speed car with a Jerico and runs low 12's and high elevens with a best time of 11.86 on unported 62 heads. That's my two cents.

Tim Corcoran

[TinInjun]

Bob:
I have never heard of the N2O guys not recommending AvGas. You said you go to the Reno air races, well, them big boy unlimited guys use N2O in their racers. You can tell when they hit the button also, that exhaust starts pouring out the black stuff [img]/infopop/emoticons/icon_smile.gif[/img]

As for Tim mentioning that he had heard that you have to richen up the mixture, its just another one of those myths, just like "It will burn up your valves." Aircraft engines don't have any kind of magic in them that makes them run any different than any other piston engine. Anyone else get my point. [img]/infopop/emoticons/icon_wink.gif[/img]

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"Run wild with an Indian, not with the crowd in a Chevy"

[Bob Dillon]

Tinny, now I'm curious. I know of no air racer that uses juice, but nearly all use nitromethane. I suppose N20 for an aircraft makes sense, as the first use of nitrous was in the German FW-190 in WWII.
However, our local airport has 2 air racers (Strega and Dago Red, I know you've heard of THEM!) hangared there, so maybe I'll bop up next weekend and ask the mechanics.

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Jesus is coming again. Look
busy!

[TinInjun]

Bob:
Check out 'Rarebear" web site at www.rarebear.com
They use NO2. I don't know if all the unlimited racers do, but seeing the horsepower numbers that are coming out of some of their engines, my guess is they have to be running NO2.

PS- Strega,,, Dago Red,,, nah, never heard of them. [img]/infopop/emoticons/icon_wink.gif[/img]

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"Run wild with an Indian, not with the crowd in a Chevy"

[Jim Moshier]

TinInjun,
I have also heard that you had to jet your carb when you using AV Gas because of the density of the fuel? AV gas has specific formula to prevent detonation, but small aircraft also have adjustable fuel controls that allow you to go from full rich on take off to lean on cruise.

below is a great site for info
http://www.wauknet.com/douthitt/pumpgas.htm

Jim Moshier

[Bob Dillon]

Hmmm...it appears from the site that Shelton (didn't I hear he was killed or died not long ago? A year or so?) is hurting for a Wright R-3350. Those shouldn't be too hard to find, they powered both the Navy's AD-1 "Able Dog" and the B-29. Wonder if Davis-Monthan has a few B-29s left? Or maybe the confederate Air Force? Both Strega and Dago Red (P-51Ds) are now Rolls Royce Griffon powered. There's a big pile of "windowed" block out behind the hangars. :-)

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Jesus is coming again. Look
busy!

[oldgoat]

TinInjun:
I really don't want to get off the topic of AV gas,but--- when you mentioned the Strega and Dago Red it brought back memories of Pop making his own, among other things.Every Fall the Chianti which had the kick of AV gas,and at Christmas the homemade Strega was more like Jet Fuel.How we looked forward to that time of the year. Strega and Dago Red,two words that just brought back very fond memories. AL

[ichabod]

I have used 100LL AV gas(6yrs.)in both my GTO's,one with 10:75 #48 heads the other 11:1 #77 heads. The cars are street driven,never any problems. This fuel also does not breakdown for those who must store their cars in the winter. I wish I could buy it for $1.73 though, I pay $2.74 up here in ME.

[Nickv]

Here in York, PA. We have a Sunoco station that sells 100 octane un-leaded race fuel. Pump it directly into your car. Works great on my 10:1 cr motor. It's not cheap though at $3.35 a gallon.