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Is anyone using Aviation MOGAS or Avgas grade 82 UL in their Antique car's? If so has it reduced hot start and vapor locking problems? How easy is it to get?

I have a 1937 Buick that I have problems with hot start after a drive using E10 Regular gasoline from the Auto pump.

I have insulated most of the fuel lines near the engine, correct routing of line, electric pump, and have a carb Insulation block. I have not tried different fuel.

From my understanding, most all low octane gas in the U.S. has 10% Ethanol mixed in and This ethanol boils off and creates air bubbles in the fuel line.

The temperature comming off the top of the radiator is about 130 and the bottom can be as high as 200, my altitude is about 1000'.

10% ethanol Gasoline Boiling point ranges from 100 to 400 F depending on altitude

Ethanol component boiling point 173 °F

Methanol component Boiling point 148.5°F

I might try to drop my carb and line temp more by wrapping fuel lines and exhaust in ceramic tape. But it would be nice to have the correct fuel the car was designed for. 75 octane no lead.

http://forums.aaca.org/ubbthreads.php/ub...e_au#Post517443

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Try adding some kerosene to the gas. Today's gas is lighter and does not have the "heavy ends" of 1920s and 1930s gas.

Start with 1 part kerosene to 5 or 6 parts gas and see what happens. I bet the engine will start easier, run smoother and cooler, develop more power and be less prone to vapor lock.

If the engine pings check your timing, if it is set to factory specs and still pings you need to use less kerosene.

One Buick owner chimed in on a similar thread and said he ran his 1932 Buick for thousands of miles on 1 part kerosene to 3 parts gas. He drove it on tours and even towed a trailer. It worked great.

Now this was on an engine with 4.5:1 compression. I believe your engine has between 6 and 7:1 so the proportion of kerosene should be less.

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Couple of suggestions. If you are seeing air bubbles in the glass fuel pump or filter sediment bowl it is probably because you have an air leak in the fuel line. Check the line fittings on the pump, filter and carb. If there is any sign of wetness the air is leaking in there. The air bubbles can cause back pressure and restrict flow. Sometimes when the fuel gets hot it will suck air in even though the fittings won't leak fuel. Generally speaking, fuel won't boil or vaporize in an enclosed fuel line if there is no air present, However it may be hot when it gets to the carb and may receive even more heat there. It is a good idea to use some type of thread sealer and make sure all fittings are tight. Never ever use a crescent wrench on brake & fuel line fittings. An open end wrench isn't much better. You might squish the fitting out of round and loose the seal.

There is a special set of fitting wrenches available from Sears/Craftsman and other tool suppliers. I forget the proper name but they are 6-sided box wrenches with one side open enough to fit over the tubing and then move over the fitting hex. These wrenches apply pressure on 5 sides and all 6 corners making it unlikely you will squish the fitting.

I would suspect the carb base insulator if it is the old hard fiber type. After years of heat and fuel/oil soaking they can loose their insulation properties. I believe that in most applications there should also be a gasket on each side of the insulator.

Stainless steel and copper fuel line absorb heat and transfer it to the fuel. Use only steel or galvanized steel tubing. Try wrapping the fuel line with insulation. I have a couple flathead Cadillac V8's that are the worst engines for vapor lock because the carb sits in the middle of the V and it is surrounded by top-side exhaust manifolding on 3 sides of the carb. If that is bad enough the fuel line runs up from the pump on one front corner of the engine and parallel to the manifold to the back of the carb. A trick I learned is to loosely crinkle wrap a couple layers of aluminum foil around the line on hot days. The air pockets between the crinkled layers keeps the heat off the line even on hot days (and it is quick & easy to remove before the judge sees it). I haven't tried it but another product that might help is the foil wrapped fiberglass insulation you use to prevent home plumbing from freezing. The fuel flowing through the line will be cool internally if you can keep the external heat off of it, especially after you shut the engine off and the fuel stops flowing, that's when it will absorb the heat.

I don't use electric fuel pumps on my flathead Cads and I use regular modern fuel without any additive. But I learned to make sure my mechanical pump is working properly and my fittings are sealed & properly tightened, and insulate my pump to carb fuel line.

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I went back & re-read previous messages. Most 30's & 40's GM cars did have asbestos insulation wrapped around the exhaust pipe from the manifold to or below the frame. Some cars also had a metal heat shield somewhere to deflect heat off the carb. I suspect that if the engineers utilized these items 70 years ago, vapor lock may have been a problem even with the old fuels.

Are you certain it is a fuel problem? What are your symptoms?

Does it crank over slow or does it crank normally but just not fire up.

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Currently the car starts instantly when cold. After a 5-10 mile drive and shut down the heat soaks the system. I have not seen bubbles in the fuel bowl so gas bubbles must be in the carburetor or upper lines.

It then takes a minute or two of cranking and pumping the accelerator pedal to dump the fuel as soon a cold fuel hits the carburetor it starts.

I believe my carburetor is operating properly but I will re-check the line fittings. The Buick does not have any OEM heat shields around the carburetor except a new insulation block and I have the splash pan/air ducting installed.

My current operating procedure is to let the engine idle some before shut down and then open the hood to dissipate heat.

I will try the Carb shops revised starting procedure.

Since I was not around in 1937 I can not know from first hand experience if they had hard starting problems with the original gasoline. But I do have Autocar test drive reports written at the time that give performance figures and detailed reviews of the vehicle by independent test drivers and they give no indication of hard starts in these documents. Which to me would have been a major red flag for a car purchase in the 1930's.

If hard start was a major problem at the time engineering would have issued service bulletins and fixes for the problem which I can not find. So that leads me back to the gasoline.

Kerosene requires a higher temperature than E10 gasoline for combustion so a solution of the two just might solve the problem. I know jet fuel is mostly Kerosene, does AVGAS a lower concentration of Kerosene?

As fuels change in the future we antique car owners might have to become chemist in order to drive.

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My mention of the original asbestos wrap was that the engineers used that to lower heat in the engine bay to prevent vapor lock. It must have helped. You said you were considering a ceramic wrap on the exhaust and that may be a good idea.

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It was a 98 degree day here in Kansas so I took the car out for a 10 mile drive. Then shut it off and I took temperature readings. The carb temp was 160 degrees. I turned off my electric fuel pump and used the mechanical fuel pump. I then tested the Carb Kings starting procedure. It worked great. At exactly 5 seconds of cranking I pressed the accelerator pedal down 1/3 and it fired up. Thanks Carb King.

Now I'll probably try ceramic tape around the exhaust and manifolds to reduce the engine bay temperature a few degrees.

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The special wrenches referred to by Jdome are called line wrenches. Auto Zone, Home Deopt, Lowes or any other place that sells hand tools will have them. They are designed to avoid rounding off the soft brass flare nut or the steel nut on fuel lines and other similar fittings by grabbing the flats on five sides instead of only two like a regular open end wrench does. The smaller the fitting, the more crucial it is to use these.

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If you buy line wrenches don't get cheap ones they are a waste of money.

When replacing brake lines or fuel lines I like to cut the line off next to the fitting and remove the fitting with a 6 point socket wrench. This saves a lot of fiddling around and allows you to reuse the fitting if necessary.

Use the line wrench to put the new line on.

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There is never a time when a cheap tool is good. The places I mentioned usually have good tools though. I have a set of Craftsman line wrenches that I bought close to 35 years ago, and most of my hand tools are Snap-On that I bought upon graduating from Vo-Tech in '72. Good tools last forever.

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  • 2 weeks later...

Regarding hot start, I'd previously seen Carbking's procedure and can also attest that it works with my Buick, although I'll admit that I use a push button starter. Not sure how it works with the standard accelerator-activated switch. In addition, take the transmission out of gear. The starter can spin the engine easier this way. Less inertia, I guess.

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With the accelerator actuated switch you need to depress the pedal very slowly to the point that it would activate the starter, then turn the key on. If it dosen't start right away don't move the accelerator. Just turn the key off and then on in a few seconds and repeat if necessary. Because of flooding in -50 degree weather I always started my Buicks this way and it works equally well in high heat.

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