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Old 08-16-2003, 01:28 PM
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How to cure vapor lock?

My 327sbc runs great till she warms up on really hot days. Fuel pressure starts at about 6psi and gradually drops down to zero(no kidding). I made sure it wasn't the gas cap. I re-routed my fuel line as far away from my exhast as I could. I am running a stock mechanical fuel pump and 3/8 fuel line. The carb is an edlebrock 1406 and the intake is an edelbrock. The engine is running about 190 on a hot summer afternoon in bumper to bumper traffic. I know its vapor lock because when I kill the motor and pull the air cleaner I can hear the fuel bubbling in the carb. After it cools down my fuel pressure returns and she runs good till the heat comes back.

Are higher performance (i.e. more expensive) fuel pumps less prone to this crap? would a carb spacer help? Am I stuck with no other aleternative than to install an electric fuel pump?

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Old 08-16-2003, 01:37 PM
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I once had a chevy suburban that did the same thing, tried wrapping the fuel line, old wooden clothes pins, everything possible, then one day the fuel gauge quit and I had to remove the tank, and there was the problem, someone had at one time put a fuel additive in the gas and the "sock" on the tank pickup was melted together, its a wonder any fuel at all would go thru what was left, replaced the entire unit and had gauge function and no more "vapor lock" problems.
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Old 08-16-2003, 01:48 PM
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Thanks Bob. I dropped the tank and inspected it when I dropped the new motor in. It looked pretty clean in there. This is on my 54' Chevy so I was really worried about rust. I didn't see any though. Because of the bubbling in the carb I'm pretty sure the fuel is boiling and the pump just cant pump it any longer.
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Old 08-16-2003, 01:53 PM
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Do you have a return line?
That would help keep fuel circulating and not have a chance to heat up at low speeds.
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Old 08-16-2003, 03:18 PM
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i'd try a spacer before i went with the electric pump..... just make sure you get the right one, something about the spread bore affecting the plenum air flow if the spacer ain't just right...or something or other..... some one help me out here.....
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Old 08-24-2003, 05:04 PM
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When I shut the engine down I can hear the fuel bubbling in the float bowls of my 1406 edelbrock carb. I noticed several folks have suggested a carb / manifold spacer plate. I was wondering which type of plate would be best? (phenolic or the Micarda/wood style) Would the spacer need 4 separate holes, 2 oval holes or one big hole? Also, which is the better line to run between the mechanical fuel pump steel or rubber tubing?
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Old 08-24-2003, 05:50 PM
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You might try some of the heat wrap that SUMMIT RACING or JEG'S sells for fuel lines. It is a foil material with a VELCRO backing so that it is easily installed w/o removing the fuel line.

EDLEBROCK makes a 1/4" thick insulated gasket that might also help insulate the carburetor from the manifold heat.

You would want the four hole spacer if that's the route you chose to take rather than an insulated gasket. The wood spacers are supposed to be the best heat resistant material, but the newer phenolic spacers are also good. Stay away from the aluminum spacers as they will just transfer the heat from manifold to carburetor.

If you do this in steps you may avoid installing an electric fuel pump which may have its own inherent problems, such as noise and being prone to failure unless you submerge it in the gas tank for cooling.
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Old 08-24-2003, 06:16 PM
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Dont get fooled into buying one of those plastic POS that a lot of places call phonelic but theyre not.

If you want the real thing try these.

CV Products


picture of real phonelic spacer
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Old 08-24-2003, 07:22 PM
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wood is a better insulator than the phenolic, but it isn't as resistant to gas as the phenolic. and Greg is right, do not buy a pos plastic spacer. last thing you want is a gooey plastic blob oozing into your manifold.(worst case scenario)
most likely you'd end up with a vacuum leak before it got sucked into the motor
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Old 08-25-2003, 12:48 AM
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If my studying is correct, you want a four hole spacer on a dual plane manifold, and an open spacer on a single plane manifold. That phenolic stuff sounds like your best bet as far as the heat transfer goes. But, I'm no expert, so this is all I can offer.
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Old 08-29-2003, 09:43 PM
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try a fuel cooler? maybe the inline type kinda looks like a small tranny cooler. i have an electric pump and i still get real low fuel pressure in the heat. not bad going down the road but between rounds maybe 10 mins after shutting down there is no fuel pressure when its hot outside. i am thinking of trying a cool can.
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Old 08-29-2003, 11:29 PM
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We use to wrap a lot of tin foil around the fuel line to see if it was hot fuel or vapor locks etc.
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Old 08-30-2003, 04:34 PM
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I installed a carter in line electric fuel pump which is wired to a switch on the dash board. The stock mechanical fuel pump pretty much does the whole job but when the temperature soars I'll just hit the switch. It seems to work and I only run it when I need it.

Thanks to everyone for their help.
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