anyone know how many GPH we should be running with 600cfm carb and a very nicely setup 302? I know we should be around 7psi, but I am going to get a new pump, my summit pump leaks like a sieve, just curious what we actually need to keep these engines happy, and not overkill Thanks
I had pretty good luck with the Edelbrock Performer 351 mechanical pump, but swapped it out with a holley Blue electric thinking I had hesitation from it, found out it was a carb problem, not a fuel issue. STMANSER is using that mechanical pump even now, after I gave it to him, with no problems.
gph is fairly simple. you need approx 1/2 pound of gas per hp per hour. so: 300 hp uses 150 lbs/hr. assume gas weighs about 6 lbs per gallon (low side). divide into 150=25 gph. problem comes with the pumps being rated at "free flow". i usually add 40 to 50 percent to the gph answer to see what pump i need. the problems come with the size of the line and the quantity & sharpness of the bends. each bend reduces the free flow, & so does the sharper the bend. size should be at least 3/8 (-6), preferable 1/2 (-8) line, depending on hp level. how quickly your engine revs also affects your needs. sound too low? i have a 600 hp sbf in my tbird, burning alcohol. alky is about 1 pound per hp per hr. that's 600 lbs divided by 6 lbs/gal=100 gph times .4 is about 140 gph. i use a mallory 140 pump. i leave at 8psi at carb & go thru traps at just over 6 psi. i have borrowed a 250 pump and found no et improvement. yes, its probably borderline needing the 250 pump. if i had a three speed, i would probably need the 250 since the engine would rev faster, especially in 1st gear. put a good size line on it, with gentle bends, a hi flo filter, & you shoudnt need a huge pump. jmho.
and 3/8" tube the entire system. I think I was using a pump that free-flowed a gallon a minute, and actually tried to fill a gallon jug in one minute with it. I don't think a low to moderate performance car needs that. Drag maybe, but not most of our cars. I would thing a 110 gph or thereabouts should do you just fine.
I have used Carter mechanical (120 gph) pumps on a 347 Mustang that ran 10.30's at over 130 mph and on a 427 inch Windsor in my Fairlane. No problem with either one. Simple and cheap.
pumping A factory fuel pump will work fine. You have to use a 3/8" min fuel line. From inside the tank to the carb. Otherwise you could have a 1000 gal. per min pump through a 5/16" line and it ain't goin pump squat.
