Vapor lock 440 6-pack issue

[Geoff 2]

As others have said: see if you get fuel squirting from the acc pump nozzle.

Also, does the engine just stop abruptly, no change in engine note, or do you get some warning?

 

[lewtot184]

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

hopefully that's not a filter before the pump.

 

[747mopar]

I've fought this issue from day one and it's infuriating. I added a 1/2 phenolic spacer under the carb, insulated the fuel line along the headers and made noticeable improvements but it's not completely fixed. Ironically it gets better in the summer months, I believe that's do to the winter blend fuel here in Ohio having a higher ethanol level?? Unfortunately I don't have access to ethenol free fuel in my town or I'd just fill up with it and forget it.

The real problem here is much like the oil, today's oils aren't designed for flat tappet engines so we buy special oil or additives. Today's fuel is designed for EFI not resting in lines next to exhaust or in a bowl sitting on top of a 200 degree chunk of iron. I know what my plan is and that's to mimic an EFI system. Electric pump (allows the bowl to be filled with zero cranking) and a return style regulator to keep the fuel moving not allowing it to get hot. This option also removes the fuel line from being near the headers as well. It's not the easiest or cheapest option but I feel it's the only one that will 100% fix it.

A vapor separator is a good option but won't help the issue with the carbs so you'd have to really get those isolated to have complete success if going this route.

 

[68BabyBlue]

I've fought this issue from day one and it's infuriating. I added a 1/2 phenolic spacer under the carb, insulated the fuel line along the headers and made noticeable improvements but it's not completely fixed. Ironically it gets better in the summer months, I believe that's do to the winter blend fuel here in Ohio having a higher ethanol level?? Unfortunately I don't have access to ethenol free fuel in my town or I'd just fill up with it and forget it.

The real problem here is much like the oil, today's oils aren't designed for flat tappet engines so we buy special oil or additives. Today's fuel is designed for EFI not resting in lines next to exhaust or in a bowl sitting on top of a 200 degree chunk of iron. I know what my plan is and that's to mimic an EFI system. Electric pump (allows the bowl to be filled with zero cranking) and a return style regulator to keep the fuel moving not allowing it to get hot. This option also removes the fuel line from being near the headers as well. It's not the easiest or cheapest option but I feel it's the only one that will 100% fix it.

A vapor separator is a good option but won't help the issue with the carbs so you'd have to really get those isolated to have complete success if going this route.

When I owned Baby Blue, the car was set up with all the features you described, and started like modern day fuel injection under all conditions with modern day fuel. Car still had the factory vapor separator hooked up, carb spacer, insulated fuel lines away from exhaust, 40 year old Holley electric fuel pump. My current GTX is 100 percent stock, with the factory vapor separator. I now have access to ethanol free fuel. No question it helps, get 1969 type performance when using it. With ethanol gas, had to prime the carb after sitting for a few days.

 

[Some Car Guy]

I can go about a week without cold start issues in an avs. That’s the outer limit. 3 days is no problem ever.

totally stock other than the thicker spacer under the carb. It still had the factory vapor separator on the 69 440. It had the correct orfice size. The gas simply did not like the heat and they had a thin almost paper thick metal spacer under the carb. Even race gas did little to stop the problem. With the 3/8 spacer Im running 93 pump gas with whatever ethanol garbage they allow in it with no issues. I do run stabil 360 every tank to combat ethanol problems.