stalling only on highway but every time

[Bonos]

vapor lock???? is gas tank vented???
bonos

[RallySnake]

Are you using an electric fuel pump or mechanical? Have you checked your fuel pressure? Which carburetor (or FI) are you running? Are the fuel lines made with steel tubing or rubber hoses? Did you route the fuel lines near the exhaust headers? Did you use rubber insulated clamps to secure the fuel lines to the chassis?

It sounds like your fuel line is getting so hot the fuel is vaporizing. Have you tried the silver heat insulated tubing over your fuel lines near the engine? like this: Amazon.com: HeatShield 274012 Thermaflect Sleeve 1/2" ID x 3' Heat Shield Sleeve: Automotive

RS

[RICK LAKE]

choprsam Easy thing to do, roadtest car until stalls out on highway, Open gas cap and see of car starts. Open cap slowly, if you get an air sound it's vapor lock and you need a vent to allow air into the gas tank.
If you get no air sound, I am going with a spark problem. Would start with a coil issue. Where's the coil mounted on the car? If it's on the motor and is an oil filled one, it's possible it is over heating and you loose spark. After the winding cool down you have spark again. Does your car have an MSD igition module, same problem. Need to see if you have spark when car stalls. If the coil is mounted on the motor in a horizontal position, move and change to vertical. Could also be too much voltage going to coil from charging system. Might need to add a resistor to drop voltage to coil and keep around 9-12 volts to it. Rest of system can run charging voltage. You didn't say what the voltage is on the car at highway speed. Quick test, get a cheap test light and go drive, need 2 people. When problem happens, pull spark plug wire and use test light to see if you have spark and light turns on. If it does, looking at possible fuel issue. Get back to us after doing these 2 tests. I think we will have an answer for your problem. MSD 6AL boxes fail from poor or no air getting to cool them also. Have guys on here that distributor modules failing in housing. lets stay with basics. Check cap first, than check spark. Rick L.