Fuel pumps gph and PSI

SixBanger

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Maybe I could help. If you calculate amounth of rotations of pumped air of your 360 engine running 4.5 k rpm, AF 11:1(giving theoretical power of 300+). Give you an volume fuel flow of 3.3L/min to make the power. Seen this on pumped=used=no extra pressure. Max pressure 20 psi=1.3 bar. So 3.3l/min * (1.3+1) = 7.6 l/min. Give you an max fuel flow at 20 psi of 100 gph ish. So pump in that range.
 

AJ/FormS

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IIRC
The formula is ; 1/2 pound of fuel per horsepower per hour, plus reserve.
A mild 360 at 250hp would need 125pounds per hp/hr or at a fuel spec of 6pounds per gallon, I get 21 gph. This would be the maximum requirement.
The carb don't care about psi so long as it doesn't blow the float valve off at idle. And so long as 21gph gets delivered to the fuel bowl at max power. If your float valves have tiny holes, they could become the choke point, giving you a high psi, but a low gph; giving you a false security; not good.
At 300hp the result is (300x.5)/6=25gph

Hey, since we know this now, what about fuel economy?
Well if it takes 40 hp to propel your car at 60 mph; then (40x.5)/6=3.33 gph .....and at 60 mph you are traveling 60 miles in one hour... so that would be 60 miles using 3.33 gallons .... which translates to.....18 mpg.
jus saying

What about running down the track?
Well say you were able to generate the 250 hp for the entire distance and did it in 15 seconds;
(250x.5)6 =21 gallons per hour or 21/60 =.35 gallon per minute.... or .087 gallon required for the run, which is 2.85 ounces. What's that in ccs? IDK,325 maybe?
 
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80mirada

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What fuel line size? The figure missing in everyone's calculation is the loss of flow from fuel line restriction. The pumps rating for flow is usually based on a specific psi through a line of a specific size for a specific length. Some pumps are rated at their max flow which is deceptive since that is rated with no outlet restrictions
 

Aspen500

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You could also figure flow loss for every bend or elbow in the line, plus a slight loss through the filter. Too much math for me:D
 

Oldiron440

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7 miles a galon? Need big holes in the gastank to get no vacuum when accerate?? Thing is thirsty!
The Volare gets no better than 3 mpg and it doesn't matter what big block I have in it, part of it is the 4.88 gears. Personally I don't care about fuel mileage, with drag radials the car will roll smoke in 3rd gear from a stop with out touching the brakes. It will burn the tires for as long as you can keep it strait.
 

Bruceynz

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I know carbs can use a lot of gas, I experience this years ago with a ford inline 4.1 straight 6, I had some gas in a glass bottle to get engine running and I was amazed when you revved engine how much it could suck through!! Amazing video, I liked seeing that!

AJ seems this is how Holley worked it out too, they say those we pumps good for 400hp! But who knows, if it starts back firing and leaning out I will know pump to small!
 

AJ/FormS

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The FSM details a fuel flow test done right at the carb with a mechanical pump.. The engine will run fine during the test on what's in the bowl(s) as long as you don't drag yourazz . The factory does the test I think at 2000 rpm, or it mighttabin at idle; either way it won't be right for a modified engine.
In your case the electrical pump will have to put out between the aforementioned 21 and 25 gph, again, right at the carb. say you target 23gph, this would be 23/60=.38gp-minute which is 12.25 ounces in one minute. The engine does not need to be running, obviously, but voltage will affect the pump, so you might as well run it to get the alternator/charging system involved.
IMO you could just take the fuel right out the back of the regulator, at idle, it's gonna be bypassing most of the fuel anyway.
 

Bruceynz

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Well got new pump in, it's like cotton wool to my ears! Didn't notice any issues with performance on my 360 but it's not like my 360 is a 500hp monster!:D

IMG-20190824-WA0002.jpeg
 
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Bruceynz

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Car going to exhaust shop on Friday for stage 2 of noise reduction, only has one oval type baffle muffler 14" x 10", going to pop in another smaller muffler bewteen tank and leaf spring. Will keep you posted!
 
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