Hello, i have a 1966 cutlas convertible that has a 1968 455 40 over block with an over stock cam (don't know the specs) and an edelbrock carb. I will list the parts below. the car runs well and is beautiful but am having a problem which i believe is vapor lock. the car run well on the road but when driving slow as in going into a car show or in traffic it will stall and not restart. the carb has a fuel pressure gauge on the fuel rail to carb and when it happens the pressure drops to zero and if engine is allowed to cool it restarts and runs well. This has become a persistent problem and i have gone from electric pump mounted right off the fuel tank to a mechanical and now back to a better electric at the tank but still having problem!!!! I have checked the under hood temps and engine temps and all are within specks (at or below 200 at temp gauge and around 150-165 under hood) with a 180 thermostat. i am reaching out because i cannot continue driving car like this as i will get stuck.
The car has:
edelbrock 1403-1221 carb
holley 12-803 fuel pressure regulator (no fuel return to tank)
holley sniper p/n 80000100 fuel pump (mounted at fuel tank)
champion 4 core radiator
2 spall high cfm radiator fans with shroud
If carb is getting too hot i believe it has a thermal isolator at base but there is no room for anything different the air cleaner will hit the hood. If any one has any ideas they will be more than welcome. NEED HELP!!!

 

I assume you have verified the pump continues to run with no pressure?

I seriously doubt it’s vapor lock. Since the fuel is pressurized, if anything the added pressure will raise the boiling point of the fuel.

Next time it quits, remove the filler cap from the fuel tank. You might also consider adding a return line circulate fuel. That will help keep the pump cool.

 

UPDATE, I noticed when i turn key on but don't start engine the electric pump runs and the fuel pressure gauge go to 10 psi. the pressure regulator is set to 5.5psi. shouldn't the regulator not allow that? Is it possible the regulator is somehow defective? Also is there a way to install a return regulator without adding a return port to the fuel tank (this car has no return port at fuel tank) to circulate the fuel.

 

Quite possibly defective. Vapor lock from what I've seen (and I may be mistaken) usually only happens when it's hot and turned off, making it tougher to hot start. When it's running you have a steady stream of cooler fuel coming in and fuel in the bowl being used instead of sitting. As far as getting a return line setup you'd want to replace your fuel tank sending with one that does have a return port, then run a hard line up to the front of the car the same way the stock fuel lines are. Then you'll also need something up front to hook it up to.

 

Vented tank or vented cap is required, is it possible you have neither?