Just reading over some of your thread. Your car and engine look great. As Franz said I ran into the same sort of problem. I messed with my car for weeks and weeks. I couldn’t get it sorted. It would lose fuel pressure under load. Especially climbing a hill and getting on it a little bit. I finally threw in the towel after trying everything I could think of and took it down to Franz. It was good. He helped sort the problems, like an arc in my fancy spark plug wires. He resurface my fuel pump valve and we took off a fuel filter as well. I thought we got it all sorted. I got it home, and went to take it on a long drive, when the weather was really hot. Sure enough I lost fuel pressure climbing a big hill. Took the exit fuel line off of the pump and could see there was fuel bubbling in there. Cooled the pump down a bit with a soaked rag and some quality me time, sitting on the side of the road looking like a dip shit wondering why I am in this hobby. I popped off the input side of the fuel line going to the pump and blew with a good breath. A big air bubble came out. Hooked it all back up, started it up and drove it home.
I would try checking the pan line as you said and put some air pressure to it at one end and blow it into a rag at the other. See what comes out. Then add some fuel, blow again and see what comes out again. If it cleans your line take it for a cruise. If it happens again, pull the outgoing line on the fuel pump, put down a rag and see what comes out. Then if that is good check the fuel line at the carb and see what comes out. If that is fine check your float bowl height.
Those fuel pumps are adjusted by gasket spacers, also check for the correct push rod for the pump you are using. Mine seemed to pump fine, but I feel the stroker engines with higher compression my run hot enough to get the fuel pump hot enough to boil the fuel, creating the bubble that won’t make it through the fuel pump valves. Or maybe at load it just can’t pump enough fuel to those bigger carbs. I don’t know.
So if the pump is not pumping due to a bubble maybe try what I did. I went on ebay, purchased a 6 volt electric fuel pump that pumps up to 2.5 PSI. Mounted it on a fuse under the tank. I Attached it to the toggle ignition lock on my steering column. Now I can run on just the mechanical or with the electric pushing the mechanical and it is out of site. I usually just turn it on at start up and turn it off when I shut down the engine. I tested the mechanical and could still notice it failing, so I would flip on the electric and it would push cool fuel through the pump and keep the fuel from bubbling. Works great. I just wish I would have set my car up for 12 volt now instead of 6. I sometimes have issues starting it after it is warmed up and has set. Maybe I have a bad battery or a draw at the starter or generator. Hope that helps.
