Race gas vs AV gas

[Thunderlugs]

I am Considering running 100LL aviation fuel in the Hemi. Price of race gas at $13 bucks, limits the amount of drive time. Can get Av gas for less than half the price. Running a 557 cam and 11ish to 1 compression. Thoughts and opinions? Pro's ...Cons?

 

[davek]

@dadsbee might know.

 

[33 IMP]

I run 33% (roughly) avgas, with the rest pump 91/10%, in a 10.5 to one, .557 cam, iron head 440
The Arizona 100LL is cheaper than california pump 91.

 

[Jerry Hall]

Just my opinion, but I think you will be fine with AV gas. If it were a 12.5 compression race Hemi, race fuel only. I run AV gas mixed 50/50 with 90 octane ethanol free in my stock and slightly modified Hemis without issue.

 

[dadsbee]

All day long. 33% to 67%. Easy mix. Throw a 5 gallon can in and then go top the tank with 91/93.

 

[Thunderlugs]

Just my opinion, but I think you will be fine with AV gas. If it were a 12.5 compression race Hemi, race fuel only. I run AV gas mixed 50/50 with 90 octane ethanol free in my stock and slightly modified Hemis without issue.

I never had hardened seats installed, so I don't want to mix with ethanol free premium. I have read that todays 100LL, has more lead than the gas did when these cars were new. If this is factual, I'm hoping this 100LL is all I should need.

 

[Jerry Hall]

I never had hardened seats installed, so I don't want to mix with ethanol free premium. I have read that todays 100LL, has more lead than the gas did when these cars were new. If this is factual, I'm hoping this 100LL is all I should need.

I don't have hardened seats in my Hemi cars and the race fuel I have purchased around here doesn't have lead. I ran Amoco white super premium in the days these cars were new without valve train issues. I'm just saying, but do what makes you comfortable.

 

[dadsbee]

100LL has about 5 times the lead in it than 70's premium had in it. Mixing it 33/67 puts you nicely in the ball park. All 6 of my cars run great on the mix. The Hemi in the HP2 included.

 

[1967coronet]

My brother has been mixing Av fuel with 93 no alky prem . 50/50 ,
He has a high compression engine, dome pistons, with open chamber eddy heads. No issues , it's going on 2 summers now.
Damn thing smells good when running even if it's a cheb. Lol

 

[33 IMP]

To the best of my knowledge.....
Other than race gas, and avgas, there's NO non-alcohol premium or regular available in california or Arizona, other than (possibly!) a small engine shop, for gardening equipment. (I was told that, have not confirmed)

 

[dadsbee]

Still getting eth free premium up here, but only at a marina. Just put 80 gallons in my Lund. She'll be fully topped when it goes home in the Fall so I can drain it for the cars.

 

[R413]

Your engine won't be happy with straight AV gas. It will be lean. Mix it with pump gas or rejet.

It has plenty of lead so pump gas won't hurt the valve seats.

If you are bound and determined to run it straight then just put in a few gallons and see, then you can add other gas to it to get it back where it should be.

 

[Photon440]

I never had hardened seats installed, so I don't want to mix with ethanol free premium. I have read that todays 100LL, has more lead than the gas did when these cars were new. If this is factual, I'm hoping this 100LL is all I should need.

It's about on par. Levels dropped all through the 1970s but in 1970 itself the average regular leaded had 2.42 grams of lead per US gallon, while premium had up to 2.81 grams. Today's 100LL Av-Gas had a maximum allowable of 2.13 grams per gallon (.56 grams/litre). If you can find the old 100 (without LL) it is about 50% higher in lead content.

 

[Curiousyellow71]

I believe sunoco 110 race gas has 2x the lead then 100LL. Higher octane race gas 3x the lead.
Its been many years but we switched from race gas and av gas with no discernable difference racing. That was with 13.4:1 on a mid 10 sec car. . We also mixed 100LL with pump gas on lower compression engines in various amounts. Never had a issue.

Because of the lead they have been trying to ban 100LL. Get it while you can!
It's always good to check to see if you are lean or rich for whatever gas your burning.
Over time we did see gaskets shrink with av gas. But, could've done the same w race gas? Either way I have no problem running 100 LL. If your combo needs or likes a jet change...change them.

 

[RickDGTX]

For what it's worth, I don't know its exact lead content, but having been a pilot for over 40 years, I remember that "100LL" is only "low lead" compared to 130 octane aviation fuel, which is no longer available, as far as I know. At least I haven't seen of heard of any for many years. A lot of our aircraft engines, including mine, were designed to run just fine on 87 octane aviation fuel, which is also no longer available. Because of that, running straight 100LL in these engines will eventually foul the spark plugs, because of the lead content. To prevent that, there are additives (I use Alcor TCP, one ounce per 10 gallons) which prevent this problem. For the past several years, the good old EPA has been bound and determined to eliminate the 100LL aviation fuel, because, heck, we burn it and fly above people and shower them with that dangerous old lead. So far, no really good substitute has been found for those engines, and there are still many, that require it. At least not one that's commercially viable.

 

[68BabyBlue]

I don't have hardened seats in my Hemi cars and the race fuel I have purchased around here doesn't have lead. I ran Amoco white super premium in the days these cars were new without valve train issues. I'm just saying, but do what makes you comfortable.

I ran Amoco super premium as well back in the day, and never had a problem. The engine in my stock Hemi GTX didn't have hardened seats, and it was run on pump gas with no issues.

 

[stage3]

u can run AV gas in your cars but its designed to burn slower than gas station pump gas..will keep your cars from pinging on that sunday drive but dont go racing with it...

 

[wwheel]

I just looked it up and the EPA restricted the lead content in automotive fuel to 2.5 grams/gallon in 1971. It states that 100LL is now 2.1 grams/gallon as Photon states. That seems to be apples to apples to me. Yes, the lead will build up in the combustion chambers eventually. Nothing a good high speed run won't help.

 

[R413]

A local racer runs straight AVgas in his 351 Ford drag car. He was always blowing up engines and a friend said it was the av gas. I added it was the Ford parts inside, we laughed. He still runs straight avgas but has better parts and wins alot now.

 

[440 PHIXX]

I used to run 50/50 Avgas, and premium unleaded in my 440 Six Pack ‘Cuda back in the 80’s. There were a lot of magazine articles saying that the exhaust valves would recede into the non hardened 906 heads. But I’ve been daily driving the 383 in my Satellite since 2014 and just running pump 93 octane. Idk… it runs fine. I guess I’d have to tear it down to see any wear.