100 LL AV Gas and problems

[Joseph E.]

Has anyone had a bad experience when mixing 100 octane low lead aviation fuel and 93 pump octane fuel in a '66 L72? I recently tried a mix of the two fuels and found it ran fine with only marginal improvement immediately after the AV fuel was added. After letting the car sit for two weeks before taking it out again, I had a completely different experience. She was difficult to start but once it did fire the sound was horrible. I was getting popping out the side exhaust, immense amounts of fumes that made your eyes sting and an idle quality so poor that it almost would not hold and idle at all. It sounded, ran and smelled as though it were running way to fat (rich). At highway speeds it smoothed out a bit but I could still feel a miss and an occasional surge while cruising along. The poor idle quality returned once I got off the highway and back into normal traffic. By the time I got home after my 30 minute drive, the idle quality had improved to the point where it would hover around 850-900 rpm but it was definitely not running the same as it did before adding the AV fuel. Normally this car runs as smooth as you could possibly want it to and it would hold an idle with no problem at between 700 and 750 rpm. This is the first time this car ran this poorly and I have to attribute it to the use of the AV gas as nothing else had been changed on the car to cause this behavior. Do any members have any input? Thank you.

Joe Evans
#45420

[John N.]

Re: 100 LL AV Gas and problems

Has anyone had a bad experience when mixing 100 octane low lead aviation fuel and 93 pump octane fuel in a '66 L72? I recently tried a mix of the two fuels and found it ran fine with only marginal improvement immediately after the AV fuel was added. After letting the car sit for two weeks before taking it out again, I had a completely different experience. She was difficult to start but once it did fire the sound was horrible. I was getting popping out the side exhaust, immense amounts of fumes that made your eyes sting and an idle quality so poor that it almost would not hold and idle at all. It sounded, ran and smelled as though it were running way to fat (rich). At highway speeds it smoothed out a bit but I could still feel a miss and an occasional surge while cruising along. The poor idle quality returned once I got off the highway and back into normal traffic. By the time I got home after my 30 minute drive, the idle quality had improved to the point where it would hover around 850-900 rpm but it was definitely not running the same as it did before adding the AV fuel. Normally this car runs as smooth as you could possibly want it to and it would hold an idle with no problem at between 700 and 750 rpm. This is the first time this car ran this poorly and I have to attribute it to the use of the AV gas as nothing else had been changed on the car to cause this behavior. Do any members have any input? Thank you.

Joe Evans
#45420

I have used the 100LL for at least 25 years in a number of cars which I still own with CR of 9.5 to over 12.0 and have done some blending with 93 unleaded. My experience has been 100% positive.
Regards

[Don H.]

Re: 100 LL AV Gas and problems

I agree, I have ran it in my 60 FI for years. Whenever the car goes on trips, pump gas is used until I get home with no problems running the mix. Don H.

[John D.]

Re: 100 LL AV Gas and problems

You have to be careful blending the 100LL with other fuels for the 100LL to be effective. Rather a waste of money to blend such a good fuel with todays wonderful ethanol crap u know.

I was late in learning about using the av fuel as never used it before 1990. My 63, the LWC eats that stuff up for sure. My generator for my trailer loves it also. Soon my Model A 4 bangor will have it in so I don't have to worry about the ethanol going bad in couple of months and plugging the Zenith carb, etc up like it is right now.


Let me tell you what I read in Business Week May 09. Ethanol is alcohol. "The Ethanol is attacking your gas tank. Its making the old scale on the tank flake off and look out after that for sure. Means plugged up fuel system." Now this ain't me talking so don't holler. I read this. Do I believe everything I read??? Well no but it is something to think about. JD

[Jim T.]

Re: 100 LL AV Gas and problems

Joseph I would check the power valve in your Holley carb. A quick check that usually verifies the power valve has malfunctioned is to start your L72, remove the air cleaner lid and put a finger over the front vent tube of the carb. It the engine dies in a couple of seconds the power valve has ruptured and is contributing to the over rich fuel ingestion.

[Jack C.]

Re: 100 LL AV Gas and problems

100% 100LL in my 427 for 5 years, no problems, however, an old timer said "never mix um", with no real good explaination.

[Paul J.]

Re: 100 LL AV Gas and problems

Joseph I would check the power valve in your Holley carb. A quick check that usually verifies the power valve has malfunctioned is to start your L72, remove the air cleaner lid and put a finger over the front vent tube of the carb. It the engine dies in a couple of seconds the power valve has ruptured and is contributing to the over rich fuel ingestion.

Joe:

I believe that your problem's something else, not the fuel. I like Jim's answer.

Paul

[Rich G.]

Re: 100 LL AV Gas and problems

Whatever his problem is, I have the same experience with my 68 427/435. I keep it at the airport so getting 100LL is easy, but I don't use it anymore because of the terrible running after sitting. The car can sit for a month with pump 93 in it and it will run fine after starting.

As an aside, right now I have 2 Cylinders off my 4 year old Continental O-200 airplane engine due to lead fouling binding the exhaust and intake valve. This engine has only 350 hours on it since new and has a Time Between Overhaul Spec of 1800 hours. The cylinders need new seats, guides and valves. There is too much lead in this gas for motors that don't get high cylinder head temps. My small continental is on a Piper Cub with an open cowl so the front cylinders never get hot enough, I guess. There is an approved additive called TCP made by Alcor which is said to help "scavange" the lead out of the cylinders. Also, we have mixture controls in airplanes, and I will be sure to lean more aggressively. You would not believe the lead that coated the top of the piston and the entire inside of the cylinder head, except for the face of the exhaust valve. I could chip it off in sheets with my finger nail

Air cooled engines run higher cylinder head temps than water cooled engines, so it wouldn't surprise me that the lead could foul a car engine.

There used to be a fuel for airplanes called 80/87 which was perfect for the low compression engines and there was the higher lead 100. The new 100LL has less lead than the old 100 octane, but much more than the old 80/87. The old engines ran fine on regular car gas, until the idiots put alcohol in it. Now it's not legal to use in an airplane.

Rich

[Doug F.]

Re: 100 LL AV Gas and problems

i have run 100 LL / 87 pump gas at varying ratios from 100 % av gas to 50 / 50 in my vets, bb truck, mower and weed eater for 20 years with no issues

[Dale C.]

Re: 100 LL AV Gas and problems

I have being using race gas which is leaded 110 octane, a little stouter than avgas. It seems to work fine on my 68 BB C60 with A/C. In fact before using it (a fifty-fifty mix with 93 octane) I was having that hot day idle dying problem. It does better now. Maybe I should cut back to the 87 stuff as its getting strong with 110 and leaded.
Dale