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Old 03-29-2017, 02:21 PM   #1
MASTERBrian
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Mechanical Fuel Pump Size??

I've sort of asked this question before, but alas here I am again....

How do I know how many GPH I need?

Here's the deal, I have an Edelbrock 1405 Carb on a Performer Manifold. Stock Heads (with valve job), bored 60over, flat top pistons, isky 270/280 Mega Hyd Cam, HEI ignition, probably a few other things I'm forgetting. Machinist said expect about 300-330hp.

Based on other conversations, I have 2 choices:
1) Run a $135 Eddy Fuel Pump and be done (my problem is that if/when it breaks I don't want to be stranded and have to order another one of those. I prefer being setup to buy and run ANY pump off the shelf)
2) Run any off the shelf pump, realizing I'll likely spend about the same because then I need to run a regulater and a guage. (again, I like being able to just replace it on the fly if need be)

Here's the issue, I called summit about a week ago to get parts number, and start prepping for the purchase. The person I spoke with last time said, don't run the regulator/gauge, just buy the Carter Pump M4685, which puts out a max of 5.5-6.5psi and you'll be golden. He even asked HP and what was done with the engine, said I'll be fine it's a perfect fit and it's only $19 and excellent reviews. Free Flow Rate is 40gph.

I finally mounted the carb earlier this morning and buttoned up my list for the order. The person I spoke with this time said I'm crazy, that's not a big enough carb for the motor, he says I need to run a standard stock style pump, which puts out Max of 8psi and 110gph, of course Summit brand and about $55. He said absolutely don't run a regulator with a mechanical pump, if I want to regulate go electric.

I realize the Carter, somewhat goes in the face of my excuse for not going with the Eddy Pump, but seems like getting it might be easier.. I'll also admit, I like the $19 price tag and the 5 star reviews. First Rep seemed on his game, second one not so much. He also thought I needed to run a braided fuel line instead of my desire to run a solid line, his reason was engine flex....how will there be flex from Mechanical pump bolted to block up to carb, which is also basically bolted to the block.

In any case, I ended the call saying I needed to think this over.

I know I'm over thinking things most likely, but what gives....is 40 gph enough for a low 300hp sbc? Or is he right and I need to go more?

I'm hoping to get this stuff ordered today, so I can maybe get it by the weekend.
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Old 03-29-2017, 02:49 PM   #2
GASoline71
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Re: Mechanical Fuel Pump Size??

These are the mechanical Carter pumps I've been using for eons. They work perfect with a Holley carb since they run just below 7 psi. 120 gph and it has a clockable base.

https://www.summitracing.com/parts/c...make/chevrolet

With an Edelbrock you'll probably need a regulator.

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Old 03-29-2017, 03:16 PM   #3
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Re: Mechanical Fuel Pump Size??

Don't count on the eddy pump putting out only 5.5 to 6.5 psi. I've heard of them cranking out much more.
Get the cheap carter pump and a 40 buck regulator and set it at 5 psi.
Then at least in the future if your fuel pump craps out you'll still have a regulator to control the pressure.
I like to use a reg that has a max output of 5.5 psi. Easier to control that way.
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Old 03-29-2017, 03:23 PM   #4
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Re: Mechanical Fuel Pump Size??

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Originally Posted by geezer#99 View Post
Don't count on the eddy pump putting out only 5.5 to 6.5 psi. I've heard of them cranking out much more.
Get the cheap carter pump and a 40 buck regulator and set it at 5 psi.
Then at least in the future if your fuel pump craps out you'll still have a regulator to control the pressure.
I like to use a reg that has a max output of 5.5 psi. Easier to control that way.
Do you have a regulator that you like? I've looked at a bunch and the pressures seem to be up to about 5 or up to about 9psi.

Also, is 40 gph enough? Or should I just get a pump at part store? I even have the pump I pulled off the old motor, just no clue if good or not.
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Old 03-29-2017, 03:38 PM   #5
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Re: Mechanical Fuel Pump Size??

I used one like this.
https://www.summitracing.com/int/par...2518/overview/

Ran a stock pump with it, never ran out of fuel even at full warp (120 mph) and 1.5 psi pressure with a dual quad (2 carter afb's).

IIRC stock pumps put out 30 to 40 gph.

Back in the day the pontiac superduty 421's with two afb's used a stock 60 gph pump rated at 9 psi with no regulator. THey ran about 1.5 psi at the end of the quarter and never ran out of fuel. No reg needed as a little flooding at idle was ok. Only idled for short periods anyway.
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Old 03-29-2017, 04:19 PM   #6
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Re: Mechanical Fuel Pump Size??

Just thought about about this a bit more and it dawned on me, 40 gph is just under 1 gallon per minute!! I'm building a cruiser, not a drag car. How would that not be enough?

I guess if for some reason it isn't, then I'll up the pump later. I doubt this thing will see much WOT for more than a few seconds at best, just long enough to bark the tires on occasion.
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Old 03-29-2017, 04:32 PM   #7
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Re: Mechanical Fuel Pump Size??

Get the Carter pump.
I use one and I have an EDL-1405 on a 350. I had a Holley regulator inline [HLY 12-803] and set at 5.5 PSI, but when I got a pro mechanic to help with setting the engine up to pass emissions, it was the first thing he took off. So I don't use it anymore. Still have it around if fuel pressure becomes an issue.
YMMV
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Old 03-29-2017, 04:36 PM   #8
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Re: Mechanical Fuel Pump Size??

I think I'll try without the regulator then, this has been part of my problem, I can't seem to find a 1-5.5psi regulator that gets decent reviews. I see several that go from 3(4) up to 9 or so, that get decent reviews, but nothing smaller. I don't mind a few bad reviews, but....
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Old 03-29-2017, 04:55 PM   #9
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Re: Mechanical Fuel Pump Size??

Well, in order to keep this build moving I ordered the carter, but for now bypassed on a regulator, though I'd still like to have one....I think?

I just can't find one that seems to fit the bill, like I said all the ones I find the are in the MAX range of 5.5-7psi seem to have horrible reviews. I also think I'd like a gauge if I go with a regulator, so I can get an idea of what everything is doing, but again finding a regulator that will house the gauge in that range proves difficult. I'm also wanting rigid line the entire run, but I feel if I go with the gauge not on the regulator, I have to insert a barbed type of fitting and run a section of hose. So for now, I'll progress with this until I find something that foots the bill....

I'm still open to suggestions on the reg and gauge combo for a decent price.
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Old 03-29-2017, 05:05 PM   #10
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Re: Mechanical Fuel Pump Size??

If you get a 4-9 PSI type regulator, you can set the pressure with a small allen key and read it out on a good vacuum/pressure gauge [tester type, not the in-dash instrument]. EG: BoschActron p/n 855-CP7802, $15 bucks at Jegs. Doubles as a manifold vacuum for tuning the Carb.
No big deal.
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Old 03-29-2017, 08:05 PM   #11
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Re: Mechanical Fuel Pump Size??

I have always been lucky enough to not need a regulator on my Eddy carbs. I just have an off the shelf Carquest pump on my daily driver K10. It puts out 4-5 psi. All you can do is try it and see how it runs.
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Old 04-04-2017, 11:18 PM   #12
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Re: Mechanical Fuel Pump Size??

I also use an auto parts store pump on an Eddy carb. No regulator, no gauge, no problems.
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Old 09-10-2017, 12:56 PM   #13
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Re: Mechanical Fuel Pump Size??

Quote:
Originally Posted by cadillac_al View Post
I have always been lucky enough to not need a regulator on my Eddy carbs. I just have an off the shelf Carquest pump on my daily driver K10. It puts out 4-5 psi. All you can do is try it and see how it runs.
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I also use an auto parts store pump on an Eddy carb. No regulator, no gauge, no problems.
Any information on a part number for those pumps?
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Old 09-10-2017, 04:57 PM   #14
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Re: Mechanical Fuel Pump Size??

I think the standard fuel pump will easily handle that but I wonder if the 500 cfm carb is enough for that kind of HP.
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Old 09-10-2017, 05:36 PM   #15
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Re: Mechanical Fuel Pump Size??

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Originally Posted by Wrenchbender Ret View Post
I think the standard fuel pump will easily handle that but I wonder if the 500 cfm carb is enough for that kind of HP.
cubic inch X max rpm divide by 3456 = cfm
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Old 09-10-2017, 06:51 PM   #16
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Re: Mechanical Fuel Pump Size??

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I think the standard fuel pump will easily handle that but I wonder if the 500 cfm carb is enough for that kind of HP.
Edelbrock 1405 is a 600 CFM carb. I run a Carter AFB 9625 which is the same thing on my 350 V8 in a '71 GMC Jimmy 4x4.
The 1404 is the 500 CFM Edelbrock clone of the Carter AFB, and I run one on my 292 L6 in my '68 C/10 Stepside.
I run no regulators. Had one on the 350, as advised by the many ''experts'' on this forum, and when I needed a pro mechanic to sort out passing AZ emissions, he looked at it and said "Lose this thing... You don't need it."
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Old 09-10-2017, 10:22 PM   #17
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Re: Mechanical Fuel Pump Size??

I stand corrected. I thought the 600 CFM was a1406.
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Old 09-11-2017, 01:41 AM   #18
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Re: Mechanical Fuel Pump Size??

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I stand corrected. I thought the 600 CFM was a1406.
It is. The 1405 and 1406 are basically the same unit. The former is manual choke and the latter has electric choke.
Edelbrock sells them with a slightly different set up, as far as metering rods and jets go, too. One is leaner out of the box. Don't recall which.
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Old 09-14-2017, 10:30 PM   #19
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Re: Mechanical Fuel Pump Size??

Back to how much fuel pump you need - fuel consumption can be estimated using brake specific fuel consumption (BSFC), a measure of efficiency. BSFC for an average gas engine will be in the neighborhood of 0.5 lb of fuel per horsepower per hour. So 300 hp x 0.5 lb/hp-hr is 150 lb/ hr. You will see some fuel pumps rated in lb/hr, but many are rated in gal/hr. To convert, divide 150 lb/hr by 6 lb/gal (density of gasoline) to get 25 lb/hr. As pointed out earlier, the Carter pump is plenty for 300 hp. Keep in mind pump flow volume drops as pressure increases, so at 5 psi the volume will be slightly less than the rated 40 gal/hr at free flow.
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