I built a 355 with a HSR, and a adjustable fpr that is turned as far clockwise as I can turn it, I started it for the first few runs and it seems to run pretty good considering it's still untuned, but the fuel pressure gauge mounted on the passenger side rail is only reading 30-35psi, everything I've read here says mildly built 350's should run around 45psi. Also note that when I got the new fuel lines made for the HSR all they had was 3/8 hose no 5/16 like the stock return line is, so the return line is 3/8 until it threads onto the stock hard line could this be the problem?

 

Key on engine off, what's your fuel pressure? Still low? Block the return line by pinching the rubber hose, what's your fuel pressure now? Still low? Replace your fuel filter and check for rusted, kinked or damaged fuel line from tank to engine. If you still don't find your low pressure cause, could be the pump itself but pumps usually don't lose pressure per say. There is a pulsator on the pump itself, it is designed to reduce pressure spikes or pulses in the fuel system. These have been known to cause pressure problems. Either way, bad pump or pulsator, you will have to drop the tank. This is why you need to carefully check all the other possibilities so you don't needlessly create a lot of work for yourself (dropping the tank). HTH and GL!

 

Just did this same swap and today put on a Accufab adjustable regulator. Which regulator are you running?

 

i built a 350 last summer with a few mods (summit alum heads, crane 2032 cam, accel base, slp runners, 24lb injectors, hooker headers, egr delete and a couple small things) and had 40psi last summer, this summer i started it for first time in a year, and had 35 psi and hardly runs. i'm going to follow what was posted above (have been planning on doing this work all summer, but with kitchen reno, baby room, and newborn it has been rough). i also just got an afpr from southbay to replace my 28 y.o. fpr on there.