I have Edelbrock 600 and Performer 351 mechanical fuel pump. I thought I was sucking the carb dry (saw the fuel filter emptying out at times and sputtering every now and then) so I put in a pressure guage. It goes right up to 6 psi when it starts up at idle, but if I idle for a while and then drive slowly through the walmart parking lot, it starts to slowly drop down to 2 or 3 psi. Of course, if I gun it out of the parking lot, it drops a little more until it builds up pressure within 30 seconds or so. Sometimes when I gun it while passing or taking off, the pressure will drop to 4 or 5, sometimes 3 psi, but quickly build back up. Today, I gunned it from a redlight, and it started at the 3 psi, and it spit and sputtered as I took off, and by the time I hit 2nd gear, it was zeroed out. It stayed at 0 psi for about 10 seconds making all kinds of sputter (kind of embarrassing ). Once I got to 60 mph in 3rd gear, it started to rise back up. Most of the time, it stays at 6, or hovers around 5 or 6. But there are a few times when it drops. Is this all normal, or should it stay pretty close to 6 ALL THE TIME? The Edelbrock carb needs 6 psi, no more, to keep from flooding out. The pump is supposed to be matched to the carb and supply that 6 psi at all RPMs.
i would not be happy with that type of variation in fuel supply. is tank pickup okay? sounds like something restricted maybe? crimped line? can borrow a pump to swap? pickup clpgging in tank? tank vent plugged?
i run a holley blue at 8psi. can't see the gauge from inside the car. but if i hit the linkage on the carb and rev it up it dosen't fluctuate much at all. i don't think what your seeing is normal.
I had the tank off a couple years back, filled it with fishtank rocks, and shook it for a couple of days to knock off all the rust. then used a kit to etch then epoxy coat the tank. I took off the charcoal canister, all the lines to it, and the vent tubes at the top of the tank were corroded closed, so I left them alone. If the cap is not vented, then the tank is currently not vented. All the rubber lines have been replaced, and I blew out the metal lines from back to front, until it was clean. New filter, new pump 3 years ago. How do I tell if the cap is vented, and/or how do I make it vented? I will try that first and see what happens.
i dont think anything after about 1970 has a vented cap, so vent your tank and see if that fixes your problem. check for crimped lines?
Will drilling a hole in the cap, or filler tube make it vent enough to solve my problem (these being the highest point in my fuel system). Otherwise, I will have to take the tank off, drill out the venting tubes on top, and fabricate some kind of venting system, maybe with a small breather/air filter coming out on top of the tank?
first, see if an early year mav has a vented cap. if so, then get one. just drilling is not a good idea since it will dump fuel when full during acceleration (ever seen a 60's chevelle leave the line with a full tank? thats gas coming out.) vented caps are somewhat internally baffled. i put a new mustang tank in with a fresh vent and put a short length of vac hose on it to extend it foward some toward the axle. didnt run it all the way forward to the canister (lazy).
not necessarily. is that orig cap? if car had canister, then cap isnt vented. mustangs early are vented. i dont know exact year canisters started. my '72 cuda had canister on it.
The cap is original, so I guess it is not vented...right now. It will be soon. As soon as I figure out how to drill a hole in the top part of the cap without messing up the rubber seal...
