Vapor lock 440 6-pack issue

[Jeff Erwin]

I went through older threads about this, want to make sure I'm not missing something.

440 6-pack starts, idle and runs smoothly. If I stop the engine for 10 minutes or so, say to run into the store, when I return the car starts after 4-5 seconds of cranking. Normal behavior. However after running for 30 seconds or so, in gear or not, the engine will die like it's out of gas. No rough running, just dies. It will restart after about 10 seconds of cranking, then is fine after that. Very predictable behavior, happens every time. It's like I use up the fuel in the middle carb float bowl.

Tank is new, vent tubes and sender unit are new. Vacuum advance is blocked while I run down a ported vacuum issue (to high at idle), running about 12btdc at idle. Again, engine runs and idles well, starts right up cold. Float bowl levels are correct. No hesitation when accelerating.

This sounds like a classic vapor lock issue to me, just not sure what to do about it. Add an electric fuel pump? Insulate the fuel lines near the engine? Any ideas here?

 

[turbine68rt]

Are you using an oem style vapor separator? What type base gaskets?

 

[Jeff Erwin]

No vapor separator, gas line from tank to filter then to carbs. Standard Holley base gaskets came with rebuild kits.

 

[R413]

When you start it hot hold the idle to 1200 for 20-30 seconds and see what it does.

I use ethanol free fuel and it stops a lot of this type of hot restarting in all my old cars. But that gets expensive with the games of today. I have a vapor separator with a return line in the 6bbl car also.

 

[diesel_lv]

Try this.

$8 Cure For Vapor Lock

 

[dadeo]

I'd say first make sure it is running out of gas. When it stalls like that, before doing anything pull the air cleaner off and look down the center carb as you work the throttle to see if the accelerator pump is discharging fuel through the squirter. No pump shot, no gas in bowl - pump shot then it's something else.
Andy

 

[BMosely]

Just went thru this on our 440 build. Boiling gas, lean out and then getting hot in traffic. You will need the vapor separator, return fuel line, and second nipple on the sender. Wix makes the seperator, but you will need to reduce the orifice size to .060” on the return leg. I used a brass screw, turned it down to fit inside the 1/4” return side and drilled the hole. There are prebent 1/4” return lines from Mancini. If your sender does not have a return, I read that some tap the filler neck.

 

[Jeff Erwin]

I will look into this. Not sure if I have a return line already installed.

 

[dadsbee]

If you need the separator, buy one from Jeff Brown that is built correctly needing no modification. www.521restorations.com

https://521restorations.com/Fuel-vapor-separator-1968-1971-440-and-426-Hemi/

 

[Sixpactogo]

440 Six Pac cars had the 3/8" fuel line with a 1/4" return and the vapor separator for a reason. You just found it.

 

[68BabyBlue]

440 Six Pac cars had the 3/8" fuel line with a 1/4" return and the vapor separator for a reason. You just found it.

I went through the same thing with my last two stock GTXs, a 440 4bbl, and my Hemi. The return line was in place, hooking up a factory style separator cured the problem.

 

[turbine68rt]

 

[PurpleBeeper]

As mentioned, when it does this, see if the squirter still works on the center carb. You can try some insulated carb gaskets. I've used the ones with the aluminum plate, gasket, aluminum plate, gasket, etc type "stack". Also, if vapor lock, the center carb will be pretty hot to the touch

 

[Jeff Erwin]

If you need the separator, buy one from Jeff Brown that is built correctly needing no modification. www.521restorations.com

https://521restorations.com/Fuel-vapor-separator-1968-1971-440-and-426-Hemi/

Ordered. Thanks. Now I just have to figure out if I already have a return line somewhere.

 

[Jeff Erwin]

View attachment 1275541

Where is that return line going?

 

[turbine68rt]

Where is that return line going?

Connects to the 1/4" hard line back to the tank sending unit.

 

[dadsbee]

1/4" return line runs right beside the feed line along the frame rail.

 

[440+6]

And if you still have problems after a return line with a vapor separator, a quarter inch phenolic spacer between all three carbs we'll fix you up.
still fits no problem under the air Grabber if you have it.
but if you go with spacers, you need to also make a quarter inch spacer for your choke assembly.
Once i did all this about ten years ago I have had zero problems

 

[diesel_lv]

@IrwinTom , out of curiosity, why do you disagree with an inline filter w vapor separator such as the factory installed on many models. Reasoning or just don't like it?

 

[72RoadrunnerGTX]

...out of curiosity, why do you disagree with an inline filter w vapor separator such as the factory installed on many models. Reasoning or just don't like it?

I can guess, there is quite a bit of information presented in Uncle Tony’s video to disagree with IMO. Using a ECS fuel tank vent line as a return line? There is a reason the factory ran a separate return line on factory installed fuel pump vapor separator installations.