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

[toolmanmike]

I have seen it bubbling in my clear filter (that I put on to diagnose a fuel related issue) I have heard it boiling in the carb of my 318 in my Swinger. Insulating the carb from the intake with a thick gasket helps as does a return style fuel filter. (that helps more when it is running) The gas now days is puppy pee compared to what it used to be. A electric charge pump near the tank hook up to a fused momentary pushbutton switch will solve the issue both cold and hot start. Electric priming pump for fuel evaporation issues.



Gasoline doesn't have a single boiling point; instead, it's a mixture of various hydrocarbons that boil at different temperatures, ranging from approximately 90°F to 400°F (32°C to 204°C), according to the U.S. Energy Information

 

[Fran Blacker]

Typo I believe.
3.22" is the number

Brain fart on the rod length. There's a plug below pump, need an allen wrech to remove plug.

 

[Rusty knuckles]

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

How many of you have added a tank return line?

I did initially to help with the vaporlock. I don't run a return with my electric pump. A fuel regulator is advisable but I'm also not running one. My carb needle and seat holds the pressure.

 

[toolmanmike]

I did initially to help with the vaporlock. I don't run a return with my electric pump. A fuel regulator is advisable but I'm also not running one. My carb needle and seat holds the pressure.

You are lucky. A friend was having excessive pressure with his mechanical pump, bought a new one from Car Quest and it was worse. Over 10#

 

[RJ Squirrel]

Also old steel fuel line could have a pinhole in it somewhere

 

[1KoolBee]

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...

The one time I had that problem with my Bee on hot days turned out to be a crappy fuel filter.

 

[WileE]

Problem solved. You're welcome.

 

[BSB67]

When was the last time you filled the gas tank.

I have traced some fuel boiling/vapor lock issue back to high Reid Vapor Pressure winter fuel.

 

[66 Sat]

Could the carb be playing a part - heat transferring back down the fuel line?
The reason I ask is the Edelbrock AVS2 is aluminium and will heat up quickly, plus the design has the bowls right on the manifold and it can suffer its own hot starting issues.
Maybe an insulating spacer could help? Just spitballing here.

 

[BMosely]

Running a carb and today’s junk gas will require a return line back to the tank with the Wix vapor separating fuel filter. You can buy it or make it but it is a .008” orifice size I believe on the vapor return side. Search my name on the subject as I had pictures and descriptions on a previous post. Get the fuel line away from the block and distributor routing. Frame rail to pump, pump back to frame rail and vapor filter, return down rail to tank, fuel up fender and up and over to carb with heat shield. That is about the best heat defense you can play.

 

[BMosely]

Pictures. Memory is for sh*t. .060” orifice.

 

[1KoolBee]

Start with the simple/cheap stuff first so you don’t feel like an idiot later! Don’t ask me how I know!

 

[Kern Dog]

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...

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

How many of you have added a tank return line?

Here we go.
For a few years, I dealt with vapor lock in warm weather and fuel starvation after a hard run.The Holey fuel pump I had only put out 5 psi even under throttle.
I switched to a Carter mechanical fuel pump. It put out 11 psi! Too much so I put in a regulator set to 7 psi and a return line to the tank. Now the fuel is always in a loop. I've driven in 110 degree Summer heat and it hasn't vapor locked since.

 

[Geoff 2]

You do not need a return line, if you have the right pump......because when they shut off, the fuel drains back to the tank. There is no pressure build up like mech pumps have.
A Carter #4594 elec pump will solve your problem, on it's own, NOT with a mech pump in series.

 

[Kern Dog]

That is flawed logic, man.
Fuel in a loop reduces the temperature of the fuel. A one way path means that at low demand, the fuel stays near the biggest heat source of the whole car, the engine.

 

[Geoff 2]

Well explain how millions of cars performed flawlessly....without a return line.

 

[Black_Sheep]

Alcohol boils at 173.1°F, if you are running oxygenated fuel it can begin to boil at or below normal engine operating temperatures. In a high pressure fuel injection system it’s not an issue, but with carburetors the fuel system pressure is much lower and prone to vapor lock. The fix could be as simple as switching to non-oxy gas.

I struggled with vapor lock after my ‘58 build because I tucked the hard line between the fuel pump and the carb too close to the engine and it would heat soak. Making a new line with more of an air gap between the line and the engine cured it. Now I’ll only run non-oxygenated fuel, fortunately it is readily available in our area.

 

[old guys rule]

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

View attachment 1881598

Where did you get your engine paint? Been looking for turquoise for years. Thanks in advance, Dave

 

[WileE]

Well explain how millions of cars performed flawlessly....without a return line.

As well as one of my cars. I prefer the quiet gerotor style, as I posted in #27.

 

[Kern Dog]

Well explain how millions of cars performed flawlessly....without a return line.

The gasoline has changed since these cars were new.
Today's fuel evaporates much faster and therefore has a lower boiling point. If your car is all stock, you may be fine, you may not.
I had my fuel lines routed like stock and while the exhaust was nowhere near the fuel lines, I still had moments where it would heat soak after sitting or just buck and stall while idling in hot weather. The return line ended that.
The heat in the engine bay elevated the temperature of the gasoline. The return line lowered it enough to not be a problem anymore.
I'm not claiming that this is an a fix for everyone but the theory is sound.
I thought that even throttle body EFI systems used a fuel system with a return line despite having fuel pressures not much higher than carbureted cars.