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Discussion Starter #1 (Edited)
I have 66 impala with a 454 big block that has headers and a 700r4. The Carburator is a 770 4 barrel Holley brawler. When the engine is at temperature and the I let it sit and heat soak a little I'm having vapor lock and hot restart issues.

I've read different solutions:

a. fuel filter with vent
b. heat shielding on headers, fuel lines, carb spacer
c. electric fuel pump
d. replace rubber fuel lines with metal and move away from heater line...

Current Setup Picture:





I was going to start with a vented fuel filter.
Part #: FIL 3041, but then I would have to have a return line back to the tank.

Could I have the return line "T" into the vent?



Any Further suggestions?



picture just because:



 

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Ted vapor lock occurs when the gas boils. Gas begins to boil (I say begins because gas isn't a uniform fluid but a mixture of dissimilar liquids) at seventy five to ninety degrees depending upon the octane rating. That octane rating is dependent upon the amount of toluene added to the mix which has a low boiling point. That volatility in high octane fuel is what makes it go "bad" when left in a partially filled container for a week or so.

Because your mechanical pump can not suck anything but vapor your engine is starved for gas. That is why the electric fuel pump is on the list. It does't suck at all if placed below the pick-up in the tank (just think of early seventies race cars with the fuel pump almost draging the ground under the rear bumper). The electric fuel pump pressurizes the fuel line so vapor lock can not occur. To see if you have vapor lock next time it dies turn off the engine and take the air filter off to see if there is any gas in the fuel bowls..

Looking at your immaculate engine I see one issue and that is the hot water line touching the fuel line. It not only adds heat but it will work harden the polished chrome copper fuel line on your dual feed Holley as the engine vibrates on it's rubber motor mounts; causing them to crack and leak fuel.

A vented fuel filter (the return line) is used with a QuadraJet on top of a BBC by the factory, but on no other carb. The Holley carb never had a return line with a mechanical pump because it relied upon the pump maintaining low pressure (4.7 psi) on the incoming fuel line. But you will need one with an electric fuel pump which adds to the cost to convert over as they are all preset at a higher pressure (7.0 psi to 24 psi). You use a pressure regulator to drop the inlet pressure down to the five pounds and return the unused fuel to the tank with a return line.

Big Dave
 

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Oh how I hated the noise my S&W electric fuel pump made. I had to mount it on a plate with rubber isolators and then mount the plate with rubber isolators to prevent if shaking itself off the car.

Today I use a scroll pump (round aluminum mandrel with seven to nine flat blades that are slung out by centripetal force to wipe against an oval enclosure moves the fuel quietly and rapidly (it can keep up with a thousand horse motor, unlike the clacker with it's piston powered pump).

I used an Aeromotive A1000 pump, but I doubt if your motor would need that much fuel. Holley or a BG fuel pump would meet your needs. I used a Barry Grant pressure regulator and reused the factory 3/8th inch fuel line as my return line (I used a half inch hard line to supply fuel from the pump located on the frame rail).

Big Dave
 

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Discussion Starter #5
I have a couple left over pumps from other projects...

Clacker... which I'd rather not use and a bosch inline from BMWs fuel injection which is around 60psi.. I'd rather not use either.

Is there no way to keep the mechanical pump and not have vapor lock issues? I found a couple places where I moved that carry non-ethanol premium gas which I'm sure will help some.

I ordered the Metal fuel lines for a holley that will keep it away from the heat hose and the block.

Will wrapping the headers help?



 

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That system was the way the factory fed their High Performance big blocks using the factory (A/C mechanical pump).

There is nothing wrong with a mechanical pump except for the fact tat it is bolted to the block and is heated by engine oil off the timing chain. So long as it has enough capacity to keep up with your power demands I would retain it. The factory pump will feed 450 to 500 horsepower depending upon fuel line size and condition of the filters.

I used to run two Holleys on top of a tunnel ram of all the time (they work fine on the street) and I used to rev it to the moon which required even more gas. That is the reason I migrated away from a mechanical pump.

You could use the BMW EFI pump with a pressure regulator to drop the inlet pressure to five pounds (the float and needle and seat mechanism is rated to flood the carb at anything over seven psi pressure). If you do do that you will need in addition to the pressure regulator a return line to the pump to dump the excess gas back in the tank.

Big Dave
 

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Discussion Starter #7
I think I'm going to try the metal lines first... if inline tube ever mails the other 3 pieces...

Then electric pump if needed.






 

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Ted,

As Dave explained, your problem is the fuel your using. The discussion could very well have stopped with that point.

You can put all the electric pumps and regulators on the car you can find. Pressurizing the fuel doesn't cover up the fact that the fuel your using is garbage. It's clear your attempting to retain somewhat of an original look under the hood and I commend you for that. Changing to metal lines will not only help with that but is a much safer way to go.

After you get the metal lines installed go buy some good fuel! What I mean by that is fuel that has no ethanol, has sufficient octane and lead. Not sure where you live but most areas of the country have airports that sell aviation fuel. It's commonly known as 100LL (100 octane, low lead). Most places also have dealers who sell "race gas" which for most original or street cars is overkill. 100LL is less than half the cost of race gas so you'll save a bunch yet still get all the benefits tied to using good fuel. As an added bonus, the shelf life of aviation fuel can be as much as 2-3 years which tells you a lot about its quality - especially when compared to pump gas.

100LL.com will get you to the nearest dealer in your area. Hopefully there's one close by. If not, bite the bullet and buy some race gas as an experiment to see what changes. Let us know how it goes.

Keith
 

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Discussion Starter #9
I think I'm going to try the metal lines first... if inline tube ever sends over 3 pieces...

Running 100 oct gas is not a real solution for a driver, if I dragged it and it was a 700hp beast maybe.. but I just plan on driving it.

I think they sell 91 and 93 no ethanol around here I'll fill up with that too.

Then electric pump if needed.



Hard lines it is... BUT

Tell me how to fit these hard lines without having them leak?

What is the trick?

Carbs side first then pump?

Block first then Carb?

pump first then Block??

UGH...



Also no one tells you the fuel ports on the new holley brawler are 3/8 tube and inline tube sells 5/16" tube. So you need fuel bowl adapters...live and learn..




 

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Discussion Starter #10
I figured out the hard line leaks,

Start at the fuel bowls clean up all fittings with steel/wool or brillo pads and tighted as you get closer to the pump. That seemed to work. Wrapped all connections in a temp shop towel and turn the engine over till you see fuel in the bowls. No leaks or wetness on the shop towels. Remove the towels....



Took her for a short ride got to temp checked the lines 2 more times for leaks so far so good.


As for the vapor locking:
It's about 70 today so not quite testing the hot start / engine vapor lock issue but seems ok after about 20 mins.
 
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