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Hot Rods av gas

Discussion in 'The Hokey Ass Message Board' started by blackanblue, Jun 4, 2019.

  1. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    Has anyone had experience using aviation fuel raw or mixed with pump gas, years ago had a friend with a bad ass truck ran it on the track with av gas don't know what octane rating it was..Sooo I have an opportunity to by a barrel of fuel these guys are using in there pre war byplanes not hi performance. I would be using in my coup with 355 blown sbc. I know there are some avators on here so looking for opinions pro or con.
     
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  2. mohead1
    Joined: Jan 18, 2013
    Posts: 592

    mohead1
    Member

    Avgas grades are defined primarily by their octane rating. Two ratings are applied to aviation gasolines (the lean mixture rating and the rich mixture rating) which results in a multiple numbering system e.g. Avgas 100/130 (in this case the lean mixture performance rating is 100 and the rich mixture rating is 130).

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  3. john worden
    Joined: Nov 14, 2007
    Posts: 1,703

    john worden
    Member
    from iowa

    Our local Volunteer FD uses it in all of our small engines. I'm no expert on it but I think it is refined to a higher standard.
    One thing you should be concerned about though I think is how fast can you use the barrels contents before it deteriorates.
     
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  4. mohead1
    Joined: Jan 18, 2013
    Posts: 592

    mohead1
    Member

    Its made different, because they lean the mixture for cruising altitude....not sure if thats some vapor point change or what

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  5. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    My son in law has a small engine sales and service business selling lawn equipment, lawnmowers chainsaws, and such but he also sells 1 quart contaners of what he calls pure gas for the equipment and claims its good for a year without going sour but 15 plus a quart. So if I bought a 40 gallon barrel I could stretch it over the summer. Just wondering if this stuff is similar to the av gas. Planning to top up to the pump gas mayby 8 to 1 with the av gas
     
  6. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    Just googled av gas for internal combustion aircraft engines 100 ll 100 octane low lead.
     
  7. mohead1
    Joined: Jan 18, 2013
    Posts: 592

    mohead1
    Member

    That sounds like the gas they sell around here for boats....straight, no ethanol. But i think its only like 89 proof (lol, octane)

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  8. 34Larry
    Joined: Apr 25, 2011
    Posts: 1,640

    34Larry
    Member

    I had a pretty frightening experience with av gas back a few years ago. On my way to the local Friday night cruse-in I stopped in local small air field and put in a few gallons on the stuff. This was in my 425, factory dual quad '66 Riviera. Left the field and in a short mile or so started smelling gas pretty strong.:eek: Pulled over, open the hood only to see both carbs looking like Niagara Falls. :eek: Had to have it towed, tank drained, carbs rebuilt. Seems it will eat stuff, (seals, gaskets and so on). That was my experience, :(never tried it again. Be careful.
     
  9. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    89 sucks, premium here is 94 not sure on the marinas but pretty sure they gut ya on the price, no boats for me.
     
  10. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    That's what I didn't want to hear,glad there was no fire.
     
  11. There is a difference in the method used to produce avgas. It has changed so much in the last 30 years, that I can only make generalizations.
    Generally speaking, aviation fuel was formulated to be more volatile to handle operation at high altitude. There was also a difference between the summer formulation and the winter formulation, with the winter formulation being more volatile for cold weather operation. This was, and still is, a regional thing, so the formulation of the fuel you are buying, depends on where you live.
    Another thing to know, is in regard to the octane rating. For the person using aviation fuel in an automotive application, the first number, for example 100 in the 100/130 gas, is the octane rating that is the equivalent of the number of the fuel used for automotive applications. The 130 number only applies to the rich, full power requirements in aircraft engines when used at take off and other max boost applications.
    Before the 90s, there were four basic fuels, 80/87, 90/96, 100/130, and 115/145 octane. All these fuels used lead. The first change in the 90s, was the combining the when the two lower octane fuels were combined and had most of the lead removed and received the designation of 90 low lead. The 100/130 fuel was still often used by guys on race day, even though they had to be careful not to get caught running on the highway (at least in Canada) with it because the road tax was not part of he price.
    The 115/145 octane fuel is used in high performance supercharged engines, such as fighters, but also in Maritime patrol aircraft, and would have to be special ordered.
    A lot of people don't understand that a higher octane number doesn't make the fuel better. Basically, if the octane number meets the requirement of your specific engine, you are only wasting money buying the higher grade fuel.
    Another problem that a person must be made aware of, if they are going to use aviation fuel, is that if you have a catalytic converter and run leaded fuel, you will destroy the converter.
    It is such a complex subject, and the fuel differs so much by region, that a person was using the fuel in an extreme situation, (with high compression ratio, or high boost), they would probably need to do some testing to find the right fuel.
    For most track conditions, the 100/115 would be adequate.
    I hope that helps, this is a difficult subject and had to be greatly simplified. In the interest of completeness, the FAA even allowed some aircraft to operate with auto gas formulations. However, there were special requirements that had to be met.
    Bob
     
  12. mohead1
    Joined: Jan 18, 2013
    Posts: 592

    mohead1
    Member

    Thats weird.....thot AV gas had no ethanol because you dont want that to happen to an airplane carb obviously
     
  13. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member

    I used 100 octane low lead in my roadster for tuning, For record runs I used ERC 110. Slightly higher specific gravity. Went up 5 on the pill. Picked up 3 mph, which was what I needed for record. So the Ave gas was pretty good. And a lot cheaper than race gas.
     
  14. KJSR
    Joined: Mar 7, 2008
    Posts: 2,444

    KJSR
    ALLIANCE MEMBER
    from Utah
    1. Utah HAMBers

    The Avgas didn't cause that...…
     
  15. john worden
    Joined: Nov 14, 2007
    Posts: 1,703

    john worden
    Member
    from iowa

    What is gained by mixing av gas with anything else? Av gas is primo fuel so why lower the octane by diluting it with lower octane lesser quality fuel?

    Ethanol added to gas is what damages various materials in the fuel system.
     
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  16. blackanblue
    Joined: Feb 20, 2009
    Posts: 408

    blackanblue
    Member

    Thanks for the insight guys will have to ponder this a bit more.
     
  17. slowmotion
    Joined: Nov 21, 2011
    Posts: 3,276

    slowmotion
    Member

    I've been using 100LL in a high compression application going on 42 years. No ill effects.
     
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  18. spanners
    Joined: Feb 24, 2009
    Posts: 1,232

    spanners
    Member

    You're lucky you can use it. Over here you have to own a 'plane to buy it. Also, we can't use leaded race fuel anymore at the tracks.
     
  19. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,986

    BamaMav
    Member
    from Berry, AL

    We ran some back in the mid 80’s in a hot street/ strip car. Car would pick up around 5 mph and drop close to a 1/2 second on et in 1/8 mile. Those are ballpark figures, been too long to remember exactly. Iirc, it was colored blue, no idea what grade it was. We had to put it in jugs, they would sell us all we wanted but we couldn’t just pump it into the car.
     
  20. mohead1
    Joined: Jan 18, 2013
    Posts: 592

    mohead1
    Member

    .5 sec faster....wtf

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  21. David Chandler
    Joined: Jan 27, 2007
    Posts: 1,101

    David Chandler
    Member

    I have no personal experience with AV gas. I did know I guy with a Corvette who used to get it, and the shut him off. That was post 9/11 and perhaps had something to do with that? That said, my father was an MP in the Army in WW2. He was in a Jeep a lot. He claimed they ran AV gas because it was all they could get. As a result, he claimed it burned the valves in the Jeep's engines. I to this day don't understand why it would, but I don't doubt him. Perhaps the AV gas back then was different? I'd think the higher octane would help the valves, more then hurt them. Strange?
     
  22. foolthrottle
    Joined: Oct 14, 2005
    Posts: 1,111

    foolthrottle
    Member

    remember that real lead 104 octane booster?
     
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  23. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,612

    Mr48chev
    ALLIANCE MEMBER

    The local Connacos sell 90 something no alcohol gas but it is right at 4 bucks a gallon. Most of the marinas on Puget Sound have ethanol free gas but it runs around 4 bucks right now. At Poulso a couple of years ago I watched a guy fill his 32 Pacard roadster with 2 5 gallon jugs at a time going down and back up the ramp and the taking two full jugs with him. Said the ethanol had eaten the innards of his carb at least once.
     
  24. Ericnova72
    Joined: May 1, 2007
    Posts: 463

    Ericnova72
    Member

    Absolutely right....pure coincidence it happened a mile after adding the AV gas.
    Avgas is damaging to anything rubber and far more stable over time. It's been discussed ad nauseum on some of the high performance and engine sites, SpeedTalk for one, along with Bracket Talk and YellowBullet, with even fuel engineers explaining everything about it in comparison to race gas and pump gas it. Won't hurt carbs or street engines one bit.

    At the air/fuel ratio's typical in automotive use, 100/130 LL Av is about 104 octane if compared directly to a modern race gasoline.
    -You can mix cheaper lower octane pump gas with Avgas to save fuel costs if you don't need as high an octane rating(just like you can with race fuel). You get some "octane creep" when mixing leaded fuel with unleaded, the lead in the better fuel helps fortify the lower octane unleaded as a little lead goes a looong way.
    A 50/50 mix of "104" Av and 93 pump would be 98.5 octane according to the math, but due to the lead induced "octane creep" the actual octane of a 50/50 mix is roughly 99.2-99.4 octane.

    Burns too hot, only good for high altitude, too dry a fuel, burns up valves, hard on rubber or gaskets, etc are all old wives tales, a good portion of which were spread by race fuel suppliers years ago in an effort to protect their profit and sales volume.
    Search over at SpeedTalk in the Engine forum if you really want to be enlightened on the subject.
     
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  25. Pete1
    Joined: Aug 23, 2004
    Posts: 2,026

    Pete1
    Member
    from Wa.

    Before you buy a barrel, check on the sale date if you can. Av gas will last a lot longer than street gas but it still goes bad eventually. If it is over a year old, pass on it.
    I have run it in my race cars since the early 50's. Most had flathead Ford V8's. Most had 14 to 1 compression.
    Back then the highest grade was 115/145 and was purple. It was equivalent to the 115 race gas we have now.
    All that is available to the general public now is 100LL, equivalent to 104 race gas.
    Av gas is not tuned like race gas. It can be run 2 jet sizes richer and 4 degrees more advance on the dyno.
    When running av gas in older engines that ran .015 to .020 plug gaps there is a tendency for the plugs to lead foul after a period of time. You can usually get a whole race program in ok without trouble.
    One big advantage to av gas is it is about half the price of race gas.

    Av gas will work fine in small power tool engines like mowers, trimmers etc. but has a tendency to lead foul plugs unless you open the gap up some. Also, over a period of time, lead will build up on the exhaust valve stem enough to cause sticking. Some MMO in a couple tanks of gas usually cures this.
    A big advantage in this type of engine is that you can forget, (or do it on purpose) to drain the tank over the winter and the gas is still ok the next spring.
     
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  26. LM14
    Joined: Dec 18, 2009
    Posts: 1,937

    LM14
    Member Emeritus
    from Iowa

    Av gas is blended with a lower volatility to work on low RPM engines with no regard for throttle response. You can have all kinds of weird tuning issues trying to run av gas.

    Check out this short read.

    https://www.fuelexpert.co.za/canirunavgas.php

    It's not the best answer by any stretch of the imagination and mostly driven by old wives tales and wild stories. As for making a car faster by adding better fuel or av gas, if that happens it means the car wasn't properly tuned or running the wrong octane for the compression/cam combination. I've had 14:1 circle track engines that ran fine on 110 and others that required 114. It depends on the combination.

    SPark
     
  27. 03GMCSonoma
    Joined: Jan 15, 2011
    Posts: 259

    03GMCSonoma
    Member

    blackanblue, back in the 60's I drove a fuel truck in the Air Force. We had 115/145 octane fuel for reciprocating/piston engines. Some of the guys would burn it in their cars but a couple of them burned out the exhaust gaskets because it burned so hot. We had to mix it about 3:1. We would fill up our cars when we had about 1/4 tank or more. No problem. One of the posts said it was purple and that is correct. All the different grades of fuel were different colors to be sure we didn't get the mixed up when we filled our trucks and/or when we were refueling aircraft. If you use it you may have to change your timing, not sure. E-85 runs about 105/109 octane but you may not want to burn alcohol. Someone else mentioned burning valves. Again, the 115/145 may have been burning too hot for the engine. Personally, I wouldn't burn it straight but would dilute it down a little. My $.02.
     
  28. Truck64
    Joined: Oct 18, 2015
    Posts: 4,765

    Truck64
    Member
    from Ioway

    The higher the octane, the fuel actually burns slower doesn't it? Same thing kind of with lean fuel mixtures, it needs the fire lit earlier than rich fuel mixtures.

    If the engine is tuned around 85 octane pump gas, and you run 92 octane it might just hurt your wallet a little, but if it gets a big ole slug of 110 and no changes are made to the ignition timing, it's now (relatively) running a fairly retarded timing at this point, and the exhaust manifolds would start getting pretty toasty. The fuel isn't all burning in the cylinders, some of it is finishing off in the exhaust. I think that's kinda what's going on, could be wrong. It doesn't do any good in any case to run high test if the engine isn't setup for it, and may cause issues at the extreme.
     
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  29. stanlow69
    Joined: Feb 21, 2010
    Posts: 5,496

    stanlow69
    Member
    from red oak

    Scan0487.jpg People ask me if my fire hydrant is hooked up. I tell them I had to put it in when I put in my Gas pump. :)
     
  30. You have to remember that the exaust gas temperature has nothing to do with the octane of fuel. It doesn't matter what the octane is, you can still burn your valves by running too lean.
    In piston airplanes, we had a procedure to lean the fuel at cruise. The procedure was, to lean the mixture to max EGT, and then richen the mixture until the temp dropped 50 to 100 degrees. This insured enough fuel for cooling the valves. In a car engine we don't have that luxury, and even if we did, imperfect fuel distribution could result in one or two lean cylinders, which would result in burned valves. Under heavy load situations, such as takeoff, airfighting, or go around, we always used full rich.
    Bob
     
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