Vapor-Locking... the bane of my existence.

[GassMann]

Hey all,

1966 Charger with a 440 - New Edelbrock 750 AV2 carb. New mechanical fuel pump. - Total rebuild including the transmission.

In the garage, it starts and runs great. On the road, until it heats up, it runs great. Run a mile and stop for a bit and it is obviously vapor-locking. The see-through fuel filter actually bubbles. Let it sit for an hour, and it starts great. The filter sits, as it has always sat, next to the carb. An anti-vapor lock filter is part of the answer though this breed of car never had one before. Should that filter be placed BEFORE the fuel pump or after?

Any suggestions would be well received.

Thanks in advance...

 

[Belvedere408]

I wrapped my bare fuel line in insulation DEI wrap from under the engine to the mechanical pump. I haven't had the issue again, but I've also haven't been at the top of a mountain at 100 degrees since.

 

[j-c-c-62]

The topic needs to be revisited? My experience with vapor lock was hearing my dad mention it in the fifties with our 1953 flat head six Plymouth with overdrive. Seems to me gas improvements and EFI among other things has put the concern mostly out to pasture.
I am not exactly sure what it really is though.
Is it gas reaching a temperature that "boils" the gas, and the mechanical fuel pump is pumping/compressing against gas bubbles and flow is greatly reduced getting past the float valve restriction in the carburetor, therefore the engine becomes the very lean or the carb nearly runs dry? Much like a diesel when run out of fuel and has an airlock, or overheated boiled brake fluid compressibility? Seems like poor fuel, high ambient temps, high altitude, sudden high fuel demand, low fuel pressure, overheated engine, fuel lines/pump near radiant exhaust heat sources, etc would all promote the dreaded vapor lock condition of years past.
I don't know.

 

[Rusty knuckles]

I had similar issues for a long time and tried lots of tricks including the vapor canister filter and a new pump. None worked well. Ultimately I put an electric pump on it. Poof, vapor lock problems gone.

In hindsight I think my fuel pump pushrod may have been worn. But the electric pump was so nice I never bothered trying to go back to a mechanical one.

 

[dvw]

Not uncommon for clear filters to see air. If there is fuel in the filter I would question if thats the issue. When it quits does it have spark? Will it start with a spritz of carb clean in the carb? In over 50 years of building hot rods never had one vapor lock.
Doug

 

[GassMann]

I wrapped my bare fuel line in insulation DEI wrap from under the engine to the mechanical pump. I haven't had the issue again, but I've also haven't been at the top of a mountain at 100 degrees since.

HA... Well, it is 90 degrees today. But I get the same response at 70. DEI wrap? Where's your fuel filter mounted?

 

[Belvedere408]

HA... Well, it is 90 degrees today. But I get the same response at 70. DEI wrap? Where's your fuel filter mounted?

Similar to this wrap. My filter is on top of engine before carb. My setup is a 408 mild stroker with a 750 Brawler.

 

[GassMann]

The topic needs to be revisited? My experience with vapor lock was hearing my dad mention it in the fifties with our 1953 flat head six Plymouth with overdrive. Seems to me gas improvements and EFI among other things has put the concern mostly out to pasture.
I am not exactly sure what it really is though.
Is it gas reaching a temperature that "boils" the gas, and the mechanical fuel pump is pumping/compressing against gas bubbles and flow is greatly reduced getting past the float valve restriction in the carburetor, therefore the engine becomes the very lean or the carb nearly runs dry? Much like a diesel when run out of fuel and has an airlock, or overheated boiled brake fluid compressibility? Seems like poor fuel, high ambient temps, high altitude, sudden high fuel demand, low fuel pressure, overheated engine, fuel lines/pump near radiant exhaust heat sources, etc would all promote the dreaded vapor lock condition of years past.
I don't know.

Well, your right about the fuel. Today's ethanol fuels boil out and I did (mistakenly) fill the tank with an ethanol mix. AND yes, I can see it boiling in the clear filter. I burned out the ethanol, well, most of it anyway, and even with premium (non-ethanol) fuel, it still boils.

We are not in a high-altitude area... 2300'.

 

[Fran Blacker]

Check push rod length, 3.22 appox. If OK electric pump. You could buy an electric pump that the mechanical pump that will drew thru when off. Most don't and maybe a cheap brand. You plumb a pump with one way valve so when elec pump is on you have fuel pressure.

 

[GassMann]

Similar to this wrap. My filter is on top of engine before carb. My setup is a 408 mild stroker with a 750 Brawler.
View attachment 1881594

Got it... excellent. I will order some today. Thanks.

 

[Don Frelier]

HA... Well, it is 90 degrees today. But I get the same response at 70. DEI wrap? Where's your fuel filter mounted?

The filter is supposed to be vertical between the alternator and water pump housing.
Kind of behind the alternator bracket.

 

[GassMann]

Not uncommon for clear filters to see air. If there is fuel in the filter I would question if thats the issue. When it quits does it have spark? Will it start with a spritz of carb clean in the carb? In over 50 years of building hot rods never had one vapor lock.
Doug

Thanks dvw... it does have spark and wants to start. It does that giddy-up start... almost starts, but not quite, then almost but not quite. Give it a few and it starts. But once it is vapor-locked, it runs REALLY rough under load. If I let it cool down, it runs great... again.

 

[GassMann]

Check push rod length, .322 appox. If OK electric pump. You could buy an electric pump that the mechanical pump that will drew thru when off. Most don't and maybe a cheap brand. You plumb a pump with one way valve so when elec pump is on you have fuel pressure.

I thought electric pumps needed a return line to the tank?!? I think anti-vapor filters do to don't they?

 

[GassMann]

The filter is supposed to be vertical between the alternator and water pump housing.
Kind of behind the alternator bracket.

View attachment 1881598

Ah... that is NOT where I mounted it. It is on top of the OEM intake manifold. I will move it.

 

[GassMann]

Check push rod length, .322 appox. If OK electric pump. You could buy an electric pump that the mechanical pump that will drew thru when off. Most don't and maybe a cheap brand. You plumb a pump with one way valve so when elec pump is on you have fuel pressure.

Will do. Though the one I installed is much longer than .322 or do you mean .322 clearance between the rod and pump? And how does one measure that???

 

[Don Frelier]

Will do. Though the one I installed is much longer than .322 or do you mean .322 clearance between the rod and pump? And how does one measure that???

Typo I believe.
3.22" is the number

 

[RemCharger]

3.22

 

[RJ Squirrel]

New pump? Maybe you got a bad one. Also check fittings from tank to pump maybe sucking air somewhere

 

[GassMann]

Typo I believe.
3.22" is the number

That makes far more sense.

You guys are great. I have some work to do to get my baby on the road. It's been far too long under cover.

 

[GassMann]

New pump? Maybe you got a bad one. Also check fittings from tank to pump maybe sucking air somewhere

Good point RJ... I will put her up on the lift and check lines.

How many of you have added a tank return line?