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Fuel pump choice

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AlfaDon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlfaDon Quote  Post ReplyReply Direct Link To This Post Topic: Fuel pump choice
    Posted: October-30-2018 at 4:22pm
I need some advice from the forum. I'm trying to find a fuel pump for my modified motor,
I'd like to find a pump that puts out more fuel than the standard mechanical pump.

I tried an electric Airtex/Carter rotary vane pump but it was only putting out 3 psi, and the carb requires 6.5 psi. It also didn't have a vent to connect a tube to the carb. I'm curious about the need for a vent on an electric pump. Do the electric pumps really need that vent tube? Do they have a diaphragm that's subject to failure?

The other electric pumps that I've found by Holley want to be mounted by the tank because they're "pushers", but that doesn't match USCG requirements of having the pump no more than 12" away from the engine.

The other choice is to go with a mechanical pump. Carter makes a mechanical pump that puts out 50 gph. An online calculator states that for my motor all I'll need is 40 gph

Those of you with modified motors, are you happy with a mechanical pump?

Thanks,
Don
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8122pbrainard View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 4:30pm
Don,
Is this pump needed to feed the Quick Fuel 750 cfm? Just wondering which engine it's for.


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AlfaDon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlfaDon Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 4:37pm
Hi Pete,
That is the carb were talking about. I'm impressed that you remember.

The engine is a standard rotation 351W that's been bored .060 over, 10.5:1 compression with a modest cam.
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JoeinNY View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 5:00pm
I would stick with a mechanical pump if at all possible. I run an electric in mine, usually a holley blue or black marine under the tank( I say usually because they fail often enough that I have grabbed auto versions at the local parts stores occasionally to save a weekend). I went that way because I was planning to run some nitrous way back when and spent about 1k all in with pump, brackets, big AN lines, regulators, gauges, relays, wiring upgrades, and oil pressure safety switches. For my trouble I have a pump that is loud and not particularly reliable.   They fail every couple years, and more than one of them has leaked while on the way out.   I have an engine that is 410 cubic inches and runs 6k rpm- I would expect I could probably get away with a good mechanical pump with appropriately sized fuel lines.
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AlfaDon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlfaDon Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 5:09pm
Thanks. The only mechanical pumps I'm finding with the vent are made by Carter and flow 40 gph and support 400 hp. The fittings on them are 1/4" NPT which seems small. All of my tubing is 3/8" which is probably a nominal 5/16" opening in the fittings.

Holley makes some marine mechanical pumps with larger openings but the castings haven't been drilled and tapped for the vent. The other consideration is finding a pump with a different diaphragm that might stand up to Ethanol blended fuel we get in California.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 5:20pm
1/4" npt is about a half inch hole and will easily support a 7/16 or 1/2" id fuel line if you wanted.   Alcohol is generally a fact of life in fuel these days I would expect any new fuel pump to be pretty resistant.
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AlfaDon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlfaDon Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 6:03pm
I forgot that I could get an 1/4" NPT fitting x 3/8" barb and it would maintain the dimensions of the existing fuel line. Thanks. I'll report back after it's installed
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeinNY Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 6:10pm
While I am very against the possibility of gas in my bilge - my boat has had a bilge fire and it was not a good time. If you really thought you were pushing over 400 hp considering a bigger high quality pump that wasn't marine rated wouldn't be the most crazyiest thing ever. You could always drill a hole for a barb for a sight tube - either tap for an npt barb or jbweld in a smooth one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MrMcD Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 6:47pm
The Rotary Vane pump is made by Carter. Other companies buy and sell this part but Carter makes them.   For your pump to have 3.5 PSI you had a bad pump.
If I remember correctly they made two versions, one with 6-8 PSI and one with 14-16 PSI.
The higher pressure pump will not work with a carbureted engine unless you use a pressure regulator.   These pumps could move up to 100 gallons per hour so starvation is not an issue with a naturally aspirated engine.   They were OEM on most long motorhomes.
These all ran 454 Chevy or 460 Ford engines and did not starve for fuel even when these rigs pulled long mountain passes. Wide open throttle for minutes at a time.
P4601 HP   14-16 PSI, 100 gph 3/8" NPSF thread inlet and outlet
P4600 HP 6-8 PSI   100 GPH    3/8 NPSF pipe thread
P4594   6-8 PSI 1/4 " NPSF 72 GPH competition series
P4070 6-8 PSI   1/4" NPSF 72 GPH This is the pump sold OEM on motorhomes.
Far as I can tell is the same as P4594 as far as specs and fit.

Even a mechanical pump should put out 4-6 PSI factory stock and those always had enough fuel to feed a small or large block engine so I think you have a bad pump not a bad design to keep up with your flow.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 7:25pm
Don,
I'm certainly not the "motor head" like Joe and Mark are but I'm trying to understand why a mechanical won't work. As Mark mentions, they had enough to feed a big block.

BTW, I'm sure the other "motor head" Ken will be along soon!


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AlfaDon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AlfaDon Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 7:27pm
Thanks McD. I'm going to try the mechanical pump.
I appreciate all of the input
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Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 7:53pm
Originally posted by 8122pbrainard 8122pbrainard wrote:

Don,
I'm certainly not the "motor head" like Joe and Mark are but I'm trying to understand why a mechanical won't work. As Mark mentions, they had enough to feed a big block.

BTW, I'm sure the other "motor head" Ken will be along soon!


Define soon Pete

Here's the Carter mechanical pump in the link.

It has a free flow rate of 50 gph with no backpressure

I figure it'll work just fine at your power level

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8122pbrainard View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: October-30-2018 at 8:41pm
Originally posted by KENO KENO wrote:

   

Define soon Pete


26 minutes. Not bad Ken.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jonny Quest Quote  Post ReplyReply Direct Link To This Post Posted: October-31-2018 at 1:28am
+1 on what KENO says. I'm running that same Carter marine fuel pump (M60389) to feed my QuickFuel M-600. It's been a good fuel pump.

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