How do I stop vapor lock?

T
I hope there is a return line I can hook up. But, what kind of return line do you use? Like put a rubber 1/4" fuel line coming from the small port on the filter to the port on the sending unit with a 1/4" steel line between them?

Thanks, that will probably solve the issue. If not, I'll let you know.

There IS NO return line. You have to add one, re rework the vent system Read my earlier post. Either you have an old style (69/ earlier) vent up in the filler tube, or you have an evap control system with the line going up to the front. READ THE shop manual

If you don't have the evap system, you will have to add a line to the front

If you DO have the evap system, you will either have to convert the vent to the old 69 style, or else add a second line, because the line up to the front IS the tank vent on the cars with evap controls.

As I said earlier, SEVENTY is the split year. Normally, CA state cars got evap controls, 49 states got the "69 style" vent

The other things you can try is to examine the fuel tube routing up by the engine / exhaust. Maybe someone changed the routing. Maybe you have headers "made it worse". Try building a heat shield / glass insulation.....you can buy Summit, etc

Consider installing a rear mount pump.

IT ALSO might be "other problems" YOU NEED to check it out

Is the tank vent plugged? Try removing the cap

Is the tank pickup sock plugged? Supply hose from tank to tube collapsing, restriction in the supply tube?

BAD fuel pump? Again, the service manual has procedures to check out the pump