392 walbro electric fuel pump question

I agree with Mad Dart and 805moparkid. You must have a bypass line back to the tank (or at least the pump inlet) when using an EFI pump. They are positive displacement pumps, which impose a volume flow. They will build up extreme pressure if "dead-headed", making either the pump stall or a line burst.

The diagram shown (www.grumpysperformance.com/FuelFlowDiagram02a1.jpg) uses a "back-pressure regulator", so is downstream of the carb inlet. For safety, it might be smart to also have a "pressure-reducing regulator" in-line with the carburetor. That will keep the carb's needle from being forced open if the back-pressure gets too high. Simple ones have a dial knob and were sold under many brands.

I also am using the same Walbro EFI pump with a carburetor. In my case, the carb is just temporary and I plan to run EFI later, but I wanted to plumb for a carb as a backup. I didn't find a cheap back-pressure reg, as shown so made my own from a cheap Norgen relief valve (McMaster-Carr?) that I added a weaker spring, and adjusted to 6 psi using shop air. It didn't work because I measured 16 psi on my car (relief wide open), so I took out the relief valve and found I got 10 psi just in the return plumbing. I put an in-line reducing reg to control what the carb sees ~5 psi). If you get one of the $45 fuel level senders on ebay, with a 3/8" outlet and 1/4" vent tube as I did, return to the 1/4" tube and you will get ~10 psi back-pressure for your carb. Drop that with an inline reducing reg. That should hold fairly constant since the EFI pump puts out way more volume at 10 psi than your carb will ever use.

Theory - a back-pressure reg controls the upstream pressure, a pressure-reducing reg controls the downstream pressure. wikipedia is your friend.