Fuel pressure general question

[cobraboyHB]

Just got my brand spankin' new Ford Racing Boss 302 crate engine up and running. Breaking it in, and put about 50 miles on yesterday but today while on PCH, out of NOWHERE it got what I think was fuel starvation, bogging down under throttle in any gear, but runs along OK when just cruising at speed.
QUESTION: What is normal fuel pressure for mechanical pump, I always thought 5 lbs was good, and 7 was the upper limit...the Russel gauge reads 3 lbs when off, and stays fluttering at 3 when I manually rev it in the driveway. Fuel line is new from pump to filter (also new and clear).
I guess it is fuel pump...probably should get a decent Holley hi-perf mechanical. I dont want to run electric.
Carb is tweaked Demon 570, flows 650.
Timing is perfect at 16 degrees adv...probably can take a couple more degrees but waiting until it is broke in right.

[Hankl]

3 PSI would below what I would want, what does your Demon require for good operation, I'm betting 4.5 to 6.5 PSI through the whole RPM range. I'd check your filters also, if you have a fuel cell, its not unheard of them clogging with specs of foam from the fuel cell.

Hank :cool:

[cobraboyHB]

Thanks, good info. No fuel cell, standard FFR tank. I thought it was odd that it sticks at 3psi on the pressure gauge, of course no way to look at it under load unless the car was strapped to a dyno. Probably go with a good Holley 110 gph mech. pump and see if that is the ticket.

[rich grsc]

Where is your filter, before or after the pump? Dont put a filter on the suction side of a pump.

[efnfast]

carb fuel pressure is usually around 6.5-7psi

[cobraboyHB]

filter is right before the hard line to the carb, looks clean, and is brand new.

[cobraboyHB]

carb fuel pressure is usually around 6.5-7psi I am hoping it is the fuel pump, as it jumped up to 5 psi and then fell back a little...maybe diaphragm has a leak and losing suction would be my guess. Anyway I have a Holley 110 GPH mechanical coming from Summit.
ONE OTHER WEIRD THING is that the gas in the filter runs clear but when it has sat for a few hours it turns yellowish, the gas lines are braided stainless over rubber, brand new from pump to carb...could this be the rubber is bleeding color into the line??

[efnfast]

What braided stainless lines are you using? I would only trust Aeroquip's, others (e.g., Russel) are known to be crappy and weep/crack easily.

[cobraboyHB]

They are rubber with braided coverings, not true AN fittings, just Magna hose clamps to look decent, so basically rubber fuel lines, all new...just strange with the discoloration of the gas when it sits, sort of like the rubber bleeding color...I would think there is not a shelf life issue from Summit Racing. thanks for the input!, All I can do is pop in the new pump and see what flies or not, next step would be vacuum but it idles great, revs up like right now when sitting in neutral and quickly settles back to a good idle with no irregular engine sounds as would be the case with vac. leaks. Basically all brand new!

[65 Cobra Dude]

Sounds like it may be a pressure versus volume issue. What size lines are you using? I had -8 and the pump could not keep 5 lbs of pressure. I dropped down to -6 and all is well.

Henry

[cobraboyHB]

3/8" lines all the way from pump to carb hard lines, should be plenty big enough for 302 with 650 carb...I guess it could come down to carb issues if the pump doesnt fix it later this week.
Re-checked timing and all is well there.