1970 cuda vapor locking

[Tj383 cuda]

Hello
 I have a 1970 cuda 383 and it is vapor locking bad on days it is 75 degrees or hotter.It run fine on cooler day. I have checked the fuel cap and vent, it is good.I have ran all new fuel line from the tank to the carb and wrapped it in heat wrap around any place there is heat.I have tryed 4 kinds of carbs,new fuel pump.It has a M1 single plain intake on it and a 750 holley double pumper.When it is cool you can take the fuel line from the tank off the fuel pump and the gas is flowing great, but when it is ran for 20-30 minutes it will quit running and you can't get a drop of gas to the fuel pump  untill it cools off.Any help i can get would be great.THANKS

[DocMel]

I seriously doubt its vapor lock;  75 degrees, I doubt it, especially if you have changed out carbs, fuel lines, etc, double check your fuel filters   DONT forget to check the sock inside the gas tank at the fuel sender unit.
Is it new.  Is the tank clean or fuel of sludge or years of crap


If you can, safely disconnect the main fuel feed line at the fuel pump.   Then run a short fuel line from the fuel pump to a large gas can, and see if it will run ok.   DONT run a fuel filter when doing this.  The idea is to bypass the gas tank, all the fuel lines, and fuel filters/   Try to isolate the prob

If you cant do the above, Ill bet its a fuel filter or gas tank prob

Are you running an electric or mech fuel pump.   If electrical, Ill bet thats the main prob in the pump itself   

[FJ5_440]

I fought with a problem I thought was vapor lock too, but it turned out to be the fuel pump push rod was worn and wouldn't pump enough once the car got very warm.  I can't explain why it seemed to keep up when it was cool, or why it didn't just fail outright, but it was 15 bucks and might be worth a shot for you too.   

I wish I would have found that before the new sending unit, gas lines, fuel pump, vapor seperator, etc........

[Bullitt-]

If you want to completely rule in or out vapor lock run it with the gas cap off then there is no way for this to happen, so if it still does you know issues are elsewhere. 

  & Welcome to the Board 

[72cudamaan]

 

[MEK-Dangerfield]

I fought with a problem I thought was vapor lock too, but it turned out to be the fuel pump push rod was worn and wouldn't pump enough once the car got very warm.  I can't explain why it seemed to keep up when it was cool, or why it didn't just fail outright, but it was 15 bucks and might be worth a shot for you too.   

I wish I would have found that before the new sending unit, gas lines, fuel pump, vapor seperator, etc........

Ditto. I had the same pushrod problem. For some reason when it got warm, the fuel pressure would plummet. The darned thing was 1/8" shorter than the new one I put in, and that solved my problem.

This definitely doesn't sound like the classic vapor lock problem.