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Old 07-05-2010, 12:23 PM
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Fuel pump capacity vs. horsepower

Anybody have a handy quick reference chart for fuel pump capacity in GPH vs. gross horsepower? I have a 350 that makes at best 350 flywheel horsepower and am wondering that capacity of fuel pump I should get. I'm thinking mechanical type. I have a stock fuel system and Edelbrock 650 carb.

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Old 07-05-2010, 09:37 PM
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this should feed that thing

http://www.summitracing.com/parts/EDL-1721/

These fuel pumps are capable of supporting up to 600 horsepower.

Free Flow Rate 110 gph
Maximum Pressure (psi) 6 psi
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Old 07-07-2010, 05:14 PM
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I'm sure that would be way more than enough. I'm not looking for huge overkill though, and not something quite that expensive.

Nobody else has comment on this? Seems like it would be rather basic unless it's really quite an unknown thing.
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Old 07-07-2010, 06:33 PM
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Well if it helps out I am using a stock fuel pump on my 86 chevy s10 and my engine makes over 450 plus horse power and outside of taking it too a track I have never had any issues using it. I also got a Carter performance mechanical fuel pump in my 96 s10 and my 350 in it has a holley carb and makes a little more power then 350 but nothing like 400 plus and it runs like a charm and I got it from summit for about 28 bucks.

http://www.summitracing.com/parts/CRT-M6624/

That would be more then enough for your motor without being too expensive.
Eric
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Old 07-08-2010, 05:12 PM
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Thanks for your reply. I like that Carter and the price is right. I also saw the 40 GPH version:
http://www.summitracing.com/parts/CRT-M4685/

which might be about right for my application too. The extra capacity though for only $8 more might be worth it. I'll check if my local parts house carries them.
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Old 07-08-2010, 10:48 PM
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A rule of thumb is to supply 1/2 pound of fuel per HP, per hour.

Gasoline weighs about 6lb./gallon, so a 350 HP engine would use a pump that could supply the carb with 30 gph pump under all conditions.
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Old 07-09-2010, 09:58 AM
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^Right on, that's good stuff right there. Thank you.
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Old 07-09-2010, 03:53 PM
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I found the 6624 for $30 and the 4685 for $35 locally. I think I may go for the 4685 because I did a little searching and found one person who had a fuel pressure issue with the 6624 being too high which messed with his carb. Changing to the 4685 brought it down to around 6 psi which is I believe where my Edelbrock 1406 likes it, as opposed to the 8-9 psi that the 6624 was delivering. I also saw conflicting capacities for the 6624, ranging from 120 GPH on Summit's site to 23 GPH on Jeg's site. That's a big difference!
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Old 07-11-2010, 12:01 AM
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GPH ratings

The Holley catalog - mechanical fuel pumps - has some graphical illustrations of what happens to GPH flow when there is back pressure. To have a guage reading of say 5.5 psi at the carb - the pump will not be delivering the GPH they advertise for "free flow".

A Holley 80 GPH pump will deliver about 30 GPH with normal delivery (back) pressure - just right for about 300 HP (at .5 pounds per hp/hr). It has to have a satisfactory suction line size (3/8) too make this sort of delivery - so don't overlook the other parts of the system.
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Old 07-12-2010, 05:21 PM
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You are definitely right about pumps and their ratings, whether it's free flow or with restrictions like fuel lines on them. Drastically changes the ratings. That's also why I wanted the 4685 over the more common 6624. I think the 120 GPH rating of the 6624 on Summit's site is a typo, since it's rated for 23 GPH on multiple other sites. The 4685 is at least rated higher at 40 GPH which explains it's slightly higher price. The 6624 is referred to as a common SBC replacement pump when I have phoned parts houses about it so I feel the 4685 is correct in having more capacity. At this time I don't have the funds for a Holley or Edelbrock 80 GPH pump so the 4685 will have to suffice.

That all said, I bought some 3/8" fuel hose today to rig up a jerry can to supply my pump instead of my fuel tank in an effort to determine if my fuel tank pick-up is clogged or not.
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Old 07-12-2010, 05:52 PM
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AIRTEX pumps

I don't know how you sort them out for sure.....but for my FORD application, I wanted a 428 CJ or Police 428 FE pump (they will fit on the Y-block 312 too) . I found out that the AIRTEX 362 looked like, smells like and pumps like the Holley 80 GPH - and it was less than half the price. Just doesn't have chrome plating and a Holley sticker.....

The AIRTEX 4657 looks like a 300 hp 327 pump to me - $60.00 US

Later found AIRTEX 40083 that is listed for the Corvette 350 Hp 327 - $50.00 US @ Autozone

Last edited by GREENBIRD56; 07-12-2010 at 11:00 PM. Reason: missed something
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Old 07-13-2010, 04:07 AM
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Quote:
Originally Posted by SUX 2BU
Anybody have a handy quick reference chart for fuel pump capacity in GPH vs. gross horsepower? I have a 350 that makes at best 350 flywheel horsepower and am wondering that capacity of fuel pump I should get. I'm thinking mechanical type. I have a stock fuel system and Edelbrock 650 carb.
no offernce, but think about it, i have a gasser, a pantera and several corvettes. Blasting down 5 in Cal at full speed (some have 500 HP) there is no way i can empty a 20 gallon tank in less than 2 hours, more like 3 hours. so do the math-20 gals divided by 2 hours at full speed (which i have NEVER achieved) is like 10 gallons per hour. so who needs an 80, 100 or 110 GPH pump??? stock pumps work just fine.
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Old 07-13-2010, 09:25 AM
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Quote:
Originally Posted by techron
who needs an 80, 100 or 110 GPH pump???
Those are "free flow" numbers.

Most street machines can get by on a LOT less, but you have to have a system capable of delivering some minimum quantity of fuel- no matter what the conditions, and w/all the restrictions in the system taken into account.

That's why earlier, I mentioned to "use a pump that could supply the carb with 30 gph pump under all conditions" for a 350 HP engine. This assures that there will always be some amount of surplus and not the other way around.

But in order to supply that 30 gph, the pump has to be much larger to account for the aforementioned restrictions, etc.

Last edited by cobalt327; 07-13-2010 at 09:59 AM.
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Old 07-13-2010, 09:53 AM
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Math?

Did somebody up there a few steps skip math in high school????

Dyno operators give you the fuel consumption of your engine at pounds per horsepower per hour. Its usually just over .50 in normally burning mixtures.

The gasoline fuel weighs (for an easy calc) 6 pounds per gallon. So....when the engine is making 350 horsepower and burning .5 pounds per horsepower per hour - it is consuming fuel at the rate of - 175 pounds per hour - which is (175/6) = 29.17 gallons per hour. So an hour is 3,600 seconds - which means a quarter mile at 15 seconds would burn .122 gallons.

My old 11.9 second 442 never did this good on mileage - it was usually more like a gallon or two to fire up, burnout, stage, run through and return. I think the 455 just liked the smell of raw gas..........

Some engines, like my buddie's tall block 427 Chev - loved fuel so much (in certain RPM bands) that we had to put alcohol sized needle and seat assemblies in there so it could get enough pounds per hour through the itty bitty carb bowl orfices during the seconds of the run where it needed it. The whole fuel system had to be sizd for the maximum consumption situation.
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