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post #1 of 11 (permalink) Old 06-25-2019, 10:43 AM Thread Starter
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Mechanical fuel pumps

I been looking the last few days at mechanical fuel pumps for my 306 build so I can order what I need this week.

So far engine will be using a Summit 600 CFM vac secondaries with the truck running stock 5/16" fuel line. Not going insane on the 306 build, just AFR 165 renegade heads in 58 CC for 9.5:1 compression with a truck roller cam.

With that said DD2000 estimates 370 hp with shorty headers with my setup. I think more around 330 - 340 hp. Based off Holley`s math for figuring optimal GPH I come up with 25 GPH for up to 300 hp and 33 GPH for up to 400 hp.

I found that the Holley 12-833 pump that puts out 80 GPH with a 1/4 NPT fittings was going to be my go to pump but then found its 7.5 PSI where Summit lists their carb as being 5 - 7 psi.

Another option I found was a Carter M60454 which is a 120 GPH pump with 6.7 PSI.

Right now how ever I am looking at a cheaper Carter M4009 that is 40 GPH with 5.5 PSI rating. Problem is the M4009 has the old early 60`s metal canister that screws in the bottom for the fuel filter.

Has anyone ever used this pump on a considerably newer vehicle?

Im sure .5 PSI more with the Holley or the 120 GPH Carter pump would be a viable option but to me it just seems like too much more volume will just be uselessly putting more load on my engine than I need.
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post #2 of 11 (permalink) Old 06-25-2019, 11:09 AM
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Re: Mechanical fuel pumps

the load on your engine comes from the spring that sets the pressure. volume is based on the diaphram size and stroke
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post #3 of 11 (permalink) Old 06-25-2019, 05:26 PM Thread Starter
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Re: Mechanical fuel pumps

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Originally Posted by extech View Post
the load on your engine comes from the spring that sets the pressure. volume is based on the diaphram size and stroke
Really?

I didn't know that so any 6.5 psi pump will put the same amount of load no matter if its 30 GPH or 150 GPH.

That's good to know cause I been looking trying to size my pump right and didn't come across anything mentioning that. Just how to figure what your pump requirements are.
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post #4 of 11 (permalink) Old 06-26-2019, 12:09 PM
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Re: Mechanical fuel pumps

I think you are a little confused here. The "load" ( effort required to "run" the pump) varies slightly with a higher volume mechanical pump. The "potential" fuel out put varies tremendously when the GPH increases. "Pressure" ( as noted on the pump) is simply when the bypass begins to operate at low fuel demands like idle. In other words a 30gph pump will NOT have 6.5 psi at wide open throttle as the demand is higher than the supply whereas a 130gph would have much higher pressure at W.O.T. because the supply IS closer or more than the demand. Volume at 5psi out of a 5/16 hose 30gph pump would about 1/4 of a 1/2" hose at 5psi and a 130gph pump.
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post #5 of 11 (permalink) Old 06-26-2019, 12:22 PM
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Re: Mechanical fuel pumps

I used the higher performance STREET Carter many times back in the day. It was a very good pump, and back then it was fairly inexpensive. They had a 'racing' version that put out around 14 psi, but it required a regulator. The 6.7 psi is perfect.

The extra volume won't hurt anything. It won't be used unless it is needed. That is how mechanical fuel pumps work. No extra load.

If you're worried about extra load... look into the fan.
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post #6 of 11 (permalink) Old 06-26-2019, 06:43 PM Thread Starter
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Re: Mechanical fuel pumps

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Originally Posted by GT350HR View Post
I think you are a little confused here. The "load" ( effort required to "run" the pump) varies slightly with a higher volume mechanical pump. The "potential" fuel out put varies tremendously when the GPH increases. "Pressure" ( as noted on the pump) is simply when the bypass begins to operate at low fuel demands like idle. In other words a 30gph pump will NOT have 6.5 psi at wide open throttle as the demand is higher than the supply whereas a 130gph would have much higher pressure at W.O.T. because the supply IS closer or more than the demand. Volume at 5psi out of a 5/16 hose 30gph pump would about 1/4 of a 1/2" hose at 5psi and a 130gph pump.
Randy
Maybe I am confused. I know the mechanical pumps will bypass what you don't need but I was under the impression that volume wise would create a load more than a more properly sized fuel pump when it is pumping and not bypassing.

Pressure wise, I thought a 6.5 PSI would maintain a maximum of 6.5 PSI correct? Which means high demand such as WOT the pump would be filling the bowls as fast as possible not able to achieve max pressure.
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post #7 of 11 (permalink) Old 06-26-2019, 06:47 PM Thread Starter
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Re: Mechanical fuel pumps

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Originally Posted by n2omike View Post
I used the higher performance STREET Carter many times back in the day. It was a very good pump, and back then it was fairly inexpensive. They had a 'racing' version that put out around 14 psi, but it required a regulator. The 6.7 psi is perfect.

The extra volume won't hurt anything. It won't be used unless it is needed. That is how mechanical fuel pumps work. No extra load.

If you're worried about extra load... look into the fan.
This is the holley one I was looking at. https://www.summitracing.com/parts/h...view/make/ford

And this is the Carter one I am looking at now as it has a max pressure of 6.7 PSI. https://www.summitracing.com/parts/c...view/make/ford

As far as load goes, I am not seeking to eliminate high load areas for max performance. I just didn't want to have excess load where I didn't need it, such as excess load by running a high volume oil pump which isn't needed for a street motor let alone a full roller motor. Same thing with the fuel pump I was concerned with going so much larger on volume than I needed that it would act in a similar way to a high volume oil pump by putting more load on the engine.

The mechanical fan, I can live with that till I can get my 3G alternator upgrade done. That might be a year after I do my engine or more.
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post #8 of 11 (permalink) Old 06-26-2019, 07:30 PM
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Re: Mechanical fuel pumps

mechanical pumps dont bypass (as there is no return line) the simply dont move the diaphram once pressure is reached. so the pump just kind of bounces the arm on the cam untill the fuel moves. then it starts moving the diaphram again
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post #9 of 11 (permalink) Old 06-27-2019, 08:22 AM
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Re: Mechanical fuel pumps

Your concern about "load" is unwarranted. "IF" you had an engine on a dyno with a mechanical pump , ran it and then removed it in favor of an electric pump , you"might" see ONE hp difference. "Most" non racing , mechanical fuel pumps will NOT maintain 6.5 PSI at 6,000 rpm on a 300 hp engine. The fuel demand is higher than the VOLUME of a standard pump. That is why race engines use larger ( 3/8ths up to 1/2" or larger) fuel lines and high volume pumps , often with an electric fuel pump at the rear of the car.
Relating a fuel pump to an oil pump is not a fair comparison. Different fluids , pump styles , and drive styles.
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post #10 of 11 (permalink) Old 06-27-2019, 09:28 AM
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Re: Mechanical fuel pumps

Quote:
Originally Posted by Rusty_S85 View Post
This is the holley one I was looking at. https://www.summitracing.com/parts/h...view/make/ford

And this is the Carter one I am looking at now as it has a max pressure of 6.7 PSI. https://www.summitracing.com/parts/c...view/make/ford

As far as load goes, I am not seeking to eliminate high load areas for max performance. I just didn't want to have excess load where I didn't need it, such as excess load by running a high volume oil pump which isn't needed for a street motor let alone a full roller motor. Same thing with the fuel pump I was concerned with going so much larger on volume than I needed that it would act in a similar way to a high volume oil pump by putting more load on the engine.

The mechanical fan, I can live with that till I can get my 3G alternator upgrade done. That might be a year after I do my engine or more.
No experience with that Holley pump. Have had good luck with the Carter. Neither should need a regulator. That's all I've got.
Good Luck!
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post #11 of 11 (permalink) Old 06-28-2019, 02:15 PM
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Re: Mechanical fuel pumps

That Holley pump sounds a lot like the one I used when we rebuilt my engine. No problem with too much fuel pressure for my carb.

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