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Old 06-24-2005, 01:43 AM
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vapor lock

how do you prevent vapor lock , I know phenolic spacer helps, also heard second fuel filter, is there any truth to that?

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Old 06-24-2005, 01:57 AM
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Does the line pass close to an exhaust manifold? If so, shield and insulate.
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Old 06-24-2005, 01:58 AM
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I believe "vapor lock" is a condition where the fuel in the float bowls start to boil... so yes, phelonic spacers help a lot. Some would argue that surrounding engine temps would eventually get too hot and boil the fuel anyhow, but in my mind, a piece of plastic between the carb and intake manifold would prevent heat transfer. Of course, if the temps got that hot, vapor lock would be the furthest thing from my mind! I'd be more concerned about overheating and warping a cylinder head, or cheap cast pistons expanding and scoring the cylinder walls....

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Old 06-24-2005, 02:04 AM
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any other way preventing vapor lock? Ill be getting ceramic coated headers which will reduce underhood temp up to 30% but what are other small things I can do before that
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Old 06-24-2005, 02:59 AM
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Quote:
Originally Posted by sel2real
I believe "vapor lock" is a condition where the fuel in the float bowls start to boil....
Actually, the vapor which might cause a problem is present in the gasoline at all times and in all locations. Gasoline is comprised of "heavy" and "light ends," which vaporize at different temperatures. Vapor is present in the fuel tank and increases as the gasoline travels into the relatively hot engine compartment. It's only when the vapor exceeds a certain percentage of the total volume that it becomes a metering problem called "vapor lock." In modern fuel injection systems, the fuel is metered while under high pressure, thus minimizing the problem. But, with the early low pressure FI systems, the presence of vapor constituted a serious problem. During the development of a GM system in the early sixties, a gasoline-to-gasoline heat exchanger was actually installed underhood to cool the fuel before metering. Ice, from the water vapor in the atmosphere, would form on the outside of the unit during operation.

Was with a friend running his car at the strip when we realized a fuel line had been placed too close to an exhaust manifold and he was obviously going lean before the traps. Not having time to do anything else, we wrapped a rag around the line and I lifted the hood and poured water on it between rounds. Worked very well.

Last edited by BillyShope; 06-24-2005 at 07:35 AM.
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Old 06-24-2005, 06:02 AM
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i heard a clothpin on gas line helps, that was from the old school, i got no idea how it works,it may have been a joke
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Old 06-25-2005, 06:48 AM
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not sure...

my 49 Ford had cloth-pins on the fuel line when I got it. I changed to aluminum foil...it still vapor locked occasionally??


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Old 06-25-2005, 09:53 AM
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gas

There are 3 cures, the phelonic spacer probably being the most expensive. You can buy a carb heat shield, which is basically a piece of aluminum under the carb to protect it, should be the cheapest. The third is a wooden spacer.
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Old 06-25-2005, 05:53 PM
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1) relocate or insulate/heat shield fuel line whereever it gets close to heat source(usually exhaust)
2)install carb. shield or phenolic spacer
3)improve airflow under hood to reduce temps
If fuel pump is mechanical(mounted on block)problem is most likely on suction side of pump.Installation of electric pump@ tank and removal of mechanical pump will also end problem in most cases.
HTH,George
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