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Ok, I saw a post mentioning running AV fuel and needing additives for lubrication. I have friend who just got his piolot's liscence have gave me the gate code to get to the fuel at the air port, The stuff costs about $1.80 a gal and I am paying about $1.75 for 92 now, Is it a good idea run this stuff. My motor is about 10 to 1.


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RYAN REEVES
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A lot of that stuff is unleaded these days, causes the same valve seat recession as unleaded auto fuel. If it is leaded, it's out and out illegal to pump it into a car that's licensed for highway use. It's being done here and there, though. Also, it's formulated for use at high altitude so you can get hard starting problems, etc.

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From what I have read, avation fuel is formulated significantly differently than auto gasoline for reasons such as high altitude, extreme cold temps at altitude, type of lube system, etc. I have never used it nor flown an airplane, however for my (engine) bucks, I would do as with oil : use what is designed for the application.

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$ 1.75...You must live in California like me!! I have been told there is an AV gas called "Low Lead" that comes in two "colors". My buddy with a plane has moved away, so I dropped the subject. But as I remember there was some that was about like pump gas high 80's low 90's octane then there was some about 103 octane. The amount of lead in it is minute compared to the good old days, but is probably similar to the the low lead of the late 70's in Calif. If you have a car that DOES NOT say "Unleaded Fuel Only" you might be able to use Low Lead AV gas. I am often wrong (according to the wife anyway) so the legalities are, as always, up to you.
Try a 5 gal. can full on a near empty tank and see if you perform any better. The true test of an engineer is someone who argues for 2 hours about the possible outcome of a 5 minute test!
 

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You should be able to run your car on Sunoco 94 Octane. Don't you have any in CA.?
I used to mix 104 AV Gas when I had my 11:1.
If you spill it, it evaporates in seconds.
You have to also run your car richer.
If you need a valve lubricant and have access to a Shell Gas Station in the States then use it the odd time because it has a valve resession additive that works better than the original lead.

Mark
 

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Not for nothing but I remember seeing an article in one of the mags where they used racing fuel on a 10:1 motor and it actually performed worse than 92. The reasoning was that the racing fuel required alot more compression than 10:1 to allow good flame propagation or some such chem engineering stuff. Anyway, they tested it on a dyno so the power loss wasn't bs.
 

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94 octane?! We not only don't have 94, we MTBE added to the fuel. That's the oxygenated fuel. This stuff is wierd. But the politicians can put a check in a box that they are saving the earth. BTW, the MTBE is poisioning the water supply from leaking tanks and 2 stroke outboard motors...which they are trying to ban. Just a few years back we just had 91 octane.
California: No jobs, lot's of welfare recipients, but the air is cleaner for the homeless!!
 

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Forget the octane ratings. You're comparing apples to oranges when comparing avgas to automotive fuel. The flash point and and vapor pressure is all different when dealing with avgas. There are some experimental aircraft using automotive fuel, but they require special type certification from the FAA to do so. Aircraft engine designs (piston engines) are based on very old technology, and are very simple in design (no electronic, computer controlled ignitions or fuel injection systems). Most of these engines were designed in the 1940s and 1950s. Even fuel injected engines use a simple mechanical injection system. And compression ratios are surprisingly low. I just can't recommend that anyone use avgas in their cars, especially a car with an engine you have just put mega bucks and hours of sweat into.
 

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I've been running av gas 100 octane for the last 5 plus years in my 12.5:1 LS/7 the engine has never seen anything else, runs great,smells great ,and I'm getting 450hp to the rear wheels with it, oh yeah my Elky does turn 11.80 1/4 mi. et. And for $2.00 a gal. you can't go wrong, just my .02 worth

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12.5:1 LS-7 and it only goes 11.80's? No wonder you use AV gas! 11:80 cars can run on pump gas if you build it right.

[This message has been edited by hangten (edited 05-20-99).]
 

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Hangman, I guess everbody has an 11 sec car how thoughtless of me !
 

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A sub 12 second time for Manuel's car is very respectable in my opinion. I too would use at least a 100 octane gas in a 12.5-1 compression motor. Pump gas will not work with that high of compression without severly retarding the timing - and losing all of your power potential.

Is that what you meant by building a motor right and getting it into the 11's Hangten, by retarding the timing? What solution would you suggest that he use instead? Help him out with your knowledge - that's what this tech board is all about - helping others and having fun at the same time.
 

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We've run a few healthy jeeps in the dunes for years on av gas, 454 and 401's. If you have a healthy engine, you can tune it to its fullest potential, plugs are clean and motor may run a fuzz cooler. If you have something close to stock, your wasting your money. In Az, there are a lot of hot boats that run out of falcon field on there way to the lakes, turbo'd and blown.
my .02
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I'm a pilot. But not a chemist. My cessna 150 (http://members.tripod.com/~heyitsme) is STC's for Auto Gas. I've never used it but I am told that Amoco Ultra is the only stuff many pilots feel comfortable with.

Octane is a factor but there are lots of other reasons why 100LL (Low Lead) is different than autogas and it has to do with emissions. Pour some AVGAS 100LL and some autogas on your hands and feel the difference. The 100LL dries immediately and has no residue. The autogas is somewhat oily and dries slower.

Now I have used avgas in my 1600 engine VW. Keep in mind that the VW engine is very similar to an Continental or Lycoming air-cooled engine. It has less tight tolerances to allow rapid expansion and contraction and generally runs hotter.

The avgas will in your V8 work but you'll be playing with carb jetting and timing to get the most out of it. I'd stay with the hitest Sunoco 94 or Amoco Ultra and be happy.

Now on the OTHER HAND - As I've said before, when I worked as a line boy back in the early 80's, we'd drain the sumps in the fuel trucks before refilling them into a couple of buckets and run them in my bug. Make a friend of an airport line boy and let them drain some sump fuel for your car and see what happens.

It's fun to experiment


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One of my hobbies is building & flying experimental aircraft. You don't need any govt.certification to use auto fuel(or anything else for that matter). You do need a STC(supplemental type certificate) to burn auto fuel in a certified aircraft like a Cessna,Piper,Mooney,etc. For most automotive applications, Avgas is a waste of money. Spend the money for proper race gas,,,,if you really need it.
 

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100 Octane Low Lead Av Gas works just fine in the higher compression engines. It is a low lead fuel and what that means in lead content in comparison to yesterday's leaded fuel, I do not know. It runs great and has never caused any harm to my engines. I have bought auto fuel everywhere from New York to California, it has smelled like everything from rubbing alcohol to lighter fluid to real gasoline from the 70's. It all runs, some better than others. What I'm saying is that you never know what you are getting. AV gas is definitely designed to run in a larger range of extremes and I know it has a greater degree of consistency than does auto fuel. I've never heard of anyone saying that it has caused an engine problem.
I only use it on a limited basis because it is just not that convienent. I have used 108 octane leaded fuel from a local Union 76 station and it smells very similar to AV gas and it makes my 396 run fantastic. It costs $3.50/gal. AV gas runs around $2 - 2.50/gal.
Most people I know that use AV gas do a 50/50 mix with premium no-lead from the pump. You get great performance at a reasonable price. I have been flying airplanes for 20 years and driving classics for about the same. Using AV gas has never created a problem, just nice performance.
 

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What I am saying is that you dont need 12:1 to get a Chevelle into the 11's. It can be done with 10:1 motors on pump gas, its done all the time. I'm not talking about some high dollar motor either, just off the shelf parts available to anyone. If you can afford to build a LS7, then take some time to seek out the right parts. If the plan is to build a motor that sounds cool then yeah, use the LS7, because the huge duration gives it the lumpy sound. IF you want to go fast, use the better technology that we have been given by GM to your advantage. Higher lift, less duration gives better ideal quality, better flow, and better performance. Add a roller cam and increase performance even more. I have shamed many loud and lumpy big blocks in my small block Chevelle with these basic principles. It runs on pump gas, no NOS. I have ran race gas with out seeing any advantages, other that a neat smell. Save your money! Dont spend it on AV gas or race gas, spend it good quality performance technology. No, I'm not it the business, just an avid racer, who got smart by watching those who win. Thats all I'm going to say.
 
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With 10 to 1 compression, you don't need Av gas. Though it's cheaper for some reason for you, I can't see the benefit..other than the bucks. But then again, running out to the airport for a fill up can't be convenient either.

A friend of mine has 12:1 454 in a 60 Impala which he's been running on Av gas for 10 years. He's never had any problems.
 

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This doesn't help at all, but for nostalgia purposes...

Back in the early '70's (I think '71), I was working for a crop duster, and I was using 5 gal of 140 avgas per tank in my '68 elky 327.

As my dad would say - it ran like a striped ass ape (whatever that means). More appropriately, it ran like a bat out of hell! The car did run a little hotter, but I would fuel it on Saturday nite before the street drags - of course I was using 104 octane premium at the pumps too...

But then again, we ran open pipes, and everything else we could think of, and get away with.

It made a real difference - but those days are gone.

But I don't think today's avgas makes any difference, and I suspect it is worse than Premium unleaded fuel in terms of performance.

>>>Rod<<<
 
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