Mechanical fuel pumps

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Mechanical fuel pumps

Post  paperman on September 30th 2014, 9:39 am

In an big dumb off-road truck will a mechanical pump be adequate? 466, 10:1, M-6250-C460 cam, a429 heads, auto with 5.13's and 42" rubber. Victor intake but no carb yet, need to buy it. Everybody runs electric pumps and I assume thats for a reason, or maybe its because thats what everybody else does? Mechanical pumps are pretty tough and can be had at most any corner parts store. Stock says its rated at 30GPH. For basic trail rides or just playin I can see it being OK but in a deep pit or long pull of 20-30 seconds I can also see my fuel bowls going dry. Can anybody give me a guess on fuel flow in either #/ hr or GPH? I assume there must be a pretty standard number for fuel Vs. HP.

Thank you.

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Re: Mechanical fuel pumps

Post  dfree383 on September 30th 2014, 11:54 am

Their are a number if mechanical pumps avaliable that will feed your combo if that's the way you want to go.
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Re: Mechanical fuel pumps

Post  paperman on September 30th 2014, 12:12 pm

Maybe I should ask it this way, is there a reason to NOT go with a mechanical pump? Between batteries, fuses, regulators, and basic bad environment it will live in an electric pump seems more likely to fail.

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Re: Mechanical fuel pumps

Post  bigblok2000ranger on September 30th 2014, 1:23 pm

A stock fuel pump with 5/16" lines is not adequate for your combo.

There are plenty of pumps out there that will work but you will need to upgrade to a minimum 3/8" line including the pickup in the tank.

Comes down to personal choice in your case.
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Re: Mechanical fuel pumps

Post  bbf-falcon on September 30th 2014, 8:19 pm

dfree383 wrote:Their are a number if mechanical pumps avaliable that will feed your combo if that's the way you want to go.
I agree

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Re: Mechanical fuel pumps

Post  FalconEh on September 30th 2014, 8:57 pm

bigblok2000ranger wrote:A stock fuel pump with 5/16" lines is not adequate for your combo.

There are plenty of pumps out there that will work but you will need to upgrade to a minimum 3/8" line including the pickup in the tank.

Comes down to personal choice in your case.

bbf-falcon wrote:
dfree383 wrote:Their are a number if mechanical pumps avaliable that will feed your combo if that's the way you want to go.
I agree

I agree also; but will elaborate a little
You need to know the size of the carb for the GPH number you are looking for ...you definitely need to increase the the fuel line size. As for the reliability of electric fuel pumps I haven't had a pump go without warning since the Holley blue days, more times with the eccentric driven mechanical pumps that blow the seals and leak fuel, however IMO there is nothing stopping you from running both the mechanical and the electric pumps in tandem when you flip the toggle on the elec pump it pushes the fuel from the tank with constant pressure and primes the mechanical pump before it starts, preserving the seals...if one dies no loss either are capable of the job...JMO
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You need a better quality mechanical pump

Post  manofmerc on October 1st 2014, 4:43 am

I instead of a parts store pump you need a high performance carter or holley mechanical fuel pump .And like others have said if your truck has 5/16 fuel lines an upgrade to 3/8 will go a long ways to provide the volume you need .I have had my 67 comet drag car at over 119 mph in the 1/4 with a mechanical fuel pump before .I have an electric pump on it now but that mechanical pump worked great for me .Check the classifieds I am listing a fuel pump for sale .Good luck to you

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Re: Mechanical fuel pumps

Post  paperman on October 1st 2014, 7:24 am

Thanks for the input guys. Ill take a look for a pump, I know the dime store ones werent what I was looking for. My commet was more geared toward if I broke at an event or trail ride I could get A pump to make it run. I hate being broke and not being able to find parts.

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Re: Mechanical fuel pumps

Post  GT300TD on October 1st 2014, 9:02 am


Doesn't a mechanical pump cost horsepower with it's drag on the cam?
Carrying a spare electric pump may also be an option.

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Re: Mechanical fuel pumps

Post  paperman on October 1st 2014, 9:24 am

GT300TD wrote:
Doesn't a mechanical pump cost horsepower with  it's drag on the cam?
Carrying a spare electric pump may also be an option.

Yep but so does the alternator, cooling fan, water pump, air compressor and other goodies under the hood. Im not an all out straight line guy. Im also not a guy with deep enough pockets to carry every part that may fail. Thats the nice side of running common or conventional parts, you can find them when you need them. Same token as the group that trys to stay with pump gas. Sure Im leaving HP on the table as I am down on compression. But I also can roll into the local Shell and top'er off and be happy Im not waiting on my drum of race gas to show up.

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Re: Mechanical fuel pumps

Post  GT300TD on October 1st 2014, 9:38 am

paperman wrote:
GT300TD wrote:
Doesn't a mechanical pump cost horsepower with  it's drag on the cam?
Carrying a spare electric pump may also be an option.

Yep but so does the alternator, cooling fan, water pump, air compressor and other goodies under the hood.  Im not an all out straight line guy.  Im also not a guy with deep enough pockets to carry every part that may fail.  Thats the nice side of running common or conventional parts, you can find them when you need them.  Same token as the group that trys to stay with pump gas.  Sure Im leaving HP on the table as I am down on compression.  But I also can roll into the local Shell and top'er off and be happy Im not waiting on my drum of race gas to show up.  

Didn't mean to upset you. I'm a low budget guy too. Just offered a suggestion!
I run a used Holley Blue with a 105 GPH $99 Jegs pump as a spare. Everything is already set up, 5 minutes to change if necessary.

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Re: Mechanical fuel pumps

Post  aquartlow on October 1st 2014, 12:11 pm

The biggest issue I went through when using a mechanical FP was vapor lock(street driven mild 466). It seems todays fuels are more susceptible to this as compared to fuel produced a few years ago(ethanol may be the biggest culprit). I upgraded to an Edelbrock 1726, still had vapor lock, once I changed the mechanical pump to a Carter P4600HP the vapor lock issues disappeared. Good luck with whatever pump you choose. Todd
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Re: Mechanical fuel pumps

Post  69F100 on October 1st 2014, 12:35 pm

aquartlow wrote:The biggest issue I went through when using a mechanical FP was vapor lock(street driven mild 466). It seems todays fuels are more susceptible to this as compared to fuel produced a few years ago(ethanol may be the biggest culprit). I upgraded to an Edelbrock 1726, still had vapor lock, once I changed the mechanical pump to a Carter P4600HP the vapor lock issues disappeared. Good luck with whatever pump you choose. Todd


Back when I had the 351c in my 69 F100 I also went to electric pump to stop the vapor lock with mechanical pump it would vapor lock at the worst times Embarassed sometimes right in the middle of town. I went with the electric so I could reroute the fuel line to get away from the heat more and it stopped the vapor lock on mine.
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Re: Mechanical fuel pumps

Post  kim on October 1st 2014, 2:57 pm

Vapor lock is/was an issue with the diaphragm mechanical pumps because of the long draw on the fuel lines from rear of vehicle to the front.  As gas gets warmer the vacuum required to flash from liquid to vapor drops.  Back in the stone age when electric pump availability was holley red or blue, and mechanical pumps were the end all....  lots of street cars ran both to beat the issue of hot summer night vapor lock.  The mechanical pump would provide volume for carb(s) the electric would facilitate a line pressure to the mechanical and prevent vapor lock.

Best advice if running mechanical pump(s) is have a fuel system that gravity feeds it.  

https://www.holley.com/products/fuel_systems/fuel_pumps_regulators_and_filters/fuel_pumps/carbureted_mechanical_pumps/parts/12-460-13

In Holleys catalogue you can get a 225+ gph pump for a small block ford, but only a 130 gph pump for the 429/460

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Re: Mechanical fuel pumps

Post  paperman on October 1st 2014, 3:38 pm

Well in some digging I see a constant that is out there of .5# of gasolin per HP per hour. Working that back lets say I make 450 HP, that means 225# of fuel per hour. Fuel is about 6#/gal. Thats about 37.5 gallons of fuel per hour, or about 5/8 gallon per minute. Seems a pump of 3X that should work fine. Stock pumps I see rated at about 30.

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Re: Mechanical fuel pumps

Post  dfree383 on October 1st 2014, 4:11 pm

450 ish hp you'll be fine with a decent performance mechanical pump.

Most guys here are running electrics because of exceeding the gpm provided by the typical mechanical stuff  What a Face

Plus pumps generally work better at pumping rather than sucking....... cheers
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