This is getting ridiculous. I had 2 summit mechanical fuel pumps go bad and now my Holley fuel pump is going bad as well. They were all internally regulated and in all cases the internal fuel pump regulator went bad after about 2-4 months causing excessive fuel pressure. The pressure was so high on the first pump it was dumping fuel into my carb. Is there something with my engine or my setup thats causing these pumps to go bad? I was just out in the garage and the pressure on my current pump is reading about 9psi. Used to only read 6psi. Looks like I'm goiing to be buying my 4th pump soon. This is a 110gph pump so its not underrated for the job. I do have a single 90 degree bend in the fuel line as it exits the fuel pump. Could that be the problem? What could be damaging these internal regulators? MAybe a clog in the line from the gas tank?

My uneducated guess would be dirt in the fuel tank.

I don't know if this is an issue but I'll throw it out there. I do have a vent hose going from the tank to a charcoal canister. There are two other nozzles on the canister. One is marked carb, the other PCV. I do have a hose running from the nozzle marked carb to the carburetor. The PCV nozzle however is plugged as I am not running a PCV. Could this be causing problems with the tank properly venting?

My uneducated guess would be dirt in the fuel tank.

Fuel tank is new as of last year, but the line from the tank to the pump is orginal. Its defintely possible the line maybe clogged.

OK here's an update. I restarted the car and the fuel pressure gauge showed 6psi. So then I figure I was hallucinating the 9psi I had seen (Wishfull thinking on my part). I took the car for a ride, checked the pressure again and it was 9psi again. Turned off the ignition for about a minute, restarted the car and then its 6 psi again. Let the car idle for about 5 minutes...still 6 psi. I'm noticing a bog issue and now I'm convinced its due to this higher fuel pressure. What i need to do is get the car to read 9 psi again and then pull the cap off the gas tank while its running and see if the fuel pressure immediatly drops to 6. This will rule out or rule in a fuel tank pressure issue.

What could be damaging these internal regulators?
Far as I know, it's not so much a regulator as it is a spring of a certain pressure that pushes on the pump diaphragm.

Sure your pressure gauge is accurate?

Far as I know, it's not so much a regulator as it is a spring of a certain pressure that pushes on the pump diaphragm.

Sure your pressure gauge is accurate?

I was thinking the same thing. My fuel gauge is on my dual feed fuel line "Edelbrock". When the engine warms up the gauge drops to zero psi. But all runs well. The little speed shop I got the line from, told me they have had lots of problems with this style of fuel gauge.

Install a pressure regulator between the pump and carburetor.

Install a pressure regulator between the pump and carburetor.

I just ordered one. I ordered this one

http://www.summitracing.com/parts/HLY-12-803/

I think I've been chasing my tail here for some time trying to tune the car when the problem all along has been inconsistent fuel pressure. Holley states right in their tech section that changes in fuel pressure require resetting the fuel bowl levels in their carbs. If thats the case then a fluctuating fuel pressure is going to reek havoc on the A/F mixture. Hopefully this fixes my issue.

No evidence that gas tank venting is my problem. I opened the tank cap when the car was running and there was no change in fuel pressure. It was running a little over 8psi today. The gauge seems to be working. I do notice that it drops when it gets hot, but I've been taking all my readings with the gauge cool.

I am going to use this pump when I build my motor and I also will use the regulator. More money, but smaller and I can go more in power of EFI and not have to change anything.

Pump
http://www.summitracing.com/parts/RPU-1500/
Regulator
http://www.summitracing.com/parts/RPU-5010/

Regulator is in and when I started the car the pressure went exactly to 6psi. Also all the jitter in the gauge needle is gone. Prior to installing the regulator, the needle would jitter back and forth about half a PSI. Now its rock solid. I didn't get a chance to retune the carb so we'll have to see if I notice a difference in performance.