Electric vs. Mechanical Fuel pump debate

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daves66valiant

daves66valiant

68 Dart 340/727:66 Signet Vert 340/5spd: 68 D100
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I'd like to open up a debate on the pros and cons of electric fuel pump vs mechanical fuel pump. Engine spec: 340 750 Holley carb 410hp

I am planning my fuel delivery system and noticed some liked the summit gig (Goody) and others tried it and didn't care for the whine (63dartman). My car is a convertible so I guess I may hear the electric pump a little more if it is under the car near the tank. The kit seems really complete and the price is nice.

I priced out both setups:

Electric kit from Summit including the tank to filter accessory and the pump the carb setup. approx $310.

Ported Mechanical Carter Hi-Flow Pump (from FBO $160) with 3/8 aluminum lines from tank to carb was about the same price if using the nice -AN fittings. Seems like more of a headache with bending and flaring the tubing, etc

What do you guys think about the fuel setup for this street car?
 
How fast are you running and whats the build? I just have a mild 318 right now, but a roller alum mag headed 360 will be shortly coming so i put the setup to feed that more than my 318. I ran alum line head to toe, rubber where rubber needed to be. Paid $68 for my new Blue pump, $30 filter, $16 for the roll of line and whatever in AN fittings. You do not have to use AN fittings, the holleys atleast have a in/out of 3/8 pipe thread. I just like working with AN, so up by the motor its all that.

I dont really care about the whine, you wanna go fast it comes with the territory. (which the 360 should be good for 11s...somewhat quick). Unless you go for the ported carter 4seconds flat has...which i rather just go electric for personal preference i guess
 
Got a 70 Dart, 340, 750 vac secondary, light spring, 4 spd with 3.91, 25 inch tires. It's drives like 4.56's because of the short tire. Car tore up a friends that runs 13.60's.

Has a stock fuel pump from Kragen and 5/16 line. Runs to 6200, normal shift points are 5800. Never runs out of fuel even at 6200 in 4th gear. I have a holley mechanical pump if needed, never saw the need to install it. Car is going to get a Proform 750DP for a test.

Personally I wouldn't spend the coin on a fuel system unless there is some need. I've seen lots of people say they are running out of fuel and it was a totally different unrelated issue.

If you aren't upgrading the fuel pickup/sending unit, it's a questionable upgrade at best. You still have a restriction right out of the tank. Don't know what's in the summit kit.

If it ain't broke, don't fix it. That's my two cents.
 
I saw your carb line setup Goody. Looks pretty clean. Looks like you have the regulator bracket kit too. Will that work on a Holley carb?

The engine build itself should get into the high 11s and low 12s. It will have a 5-speed Keisler to either 3.23s or 3.51s in the rear. I will have a new 3/8 pick-up/sending unit. Tires will be the biggest meat I can get back there, maybe 8-9" range in the uncut a-body. Power to the ground will be the biggest issue for low times. Cal-tracs would be nice. I'm not looking to be a bracket racer with a convertible. A little too dangerous but I would like to tear down the track a few times a year.
 
daves66valiant said:
I saw your carb line setup Goody. Looks pretty clean. Looks like you have the regulator bracket kit too. Will that work on a Holley carb?
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Its actually made for a holley, tweaked for my eddie. Jegs sells them under their brand

Doneeddie.gif
 
One definate advantage: With an electric system, there is no messing around trying to reprime the fuel system after your car sits all winter. I remember having to do that on my dad's 66 Charger and it sucked.:wack:


I am with Don (FBO) on this one:
G-Forces, these pumps as most fuel pumps designed for carbureted engines are designed to push fuel at relatively low pressures which are created by resistance or restriction in the fuel delivery system. When you launch and generate anywhere between 1.5 and 3 G's all the fuel in the column or fuel line is being driven back to the pump at the G force times the weight of fuel in the line. Without a pump that can overcome these forces the carburetor will temporarily run low on fuel. Will it melt down the motor, not in anything but an extreme condition, will it hurt performance, yes definitely. If you want the best possible and most consistent time slips then the pump must be able to handle the task at hand.

BSFC, so you did the calculations, weight to gallons conversion and your engine mathematically requires only 80 GPH. True, but did you account for the G force's of the fuel trying to reverse itself on launch, what about the gear ratio of 2.45:1, remember the HP formula- weight/over distance/over time?

If your fuel pump isn't up to the task it's very difficult to diagnose unless the problem is extreme and the engine stalls 20 feet off the line. Doing a plug check from a 60 foot shut down or 1st gear is pretty tough and by the time you get to the stripe the pump has recovered and the plugs look fine.

"I run a 10 second, 3500# car, Holley Blue pump and 5/16 line and it works great" ...don't even go there, I've heard this a 1000 times if I've heard it once, and as soon as we put on the correct fuel pump and lines the car cuts .2 to .5 off the ET, runs way more consistent, drops 100 degrees or more on the EGT and 10 degrees cooler at the stripe. All good things!
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Being in California we get to drive all year long. I say keep it simple run a mechanical pump. They make after market pumps that pump 110 GPM and more. Plus they are safer if you are ever in an accident. If the motor dies no more fuel blowing all over that hot engine.

Leave the electric pumps for the fuel injected and race cars you will be a lot happier

Thats my pros and cons
 
So Goody, when are you gonna bring your car down here to Ennis and run at our 500 ft altitude? Probably cut a 1/2 second off your car :thumbup:
 
superdart said:
So Goody, when are you gonna bring your car down here to Ennis and run at our 500 ft altitude? Probably cut a 1/2 second off your car :thumbup:
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Yea no kidding, it'd probably do that easily. I'm actually moving to florida in about a month or so. It outta run WELL out there :twisted:
 
I run an elec pump. I run it off of a relay, through a ferd fuel pump safety impact/rollover switch. Also running to this relay is a very very small switch hidden in reach of the driver seat to shut off said pump, for leaving the car parked. This way it also doubles as a theft deterrent. Because if your car is broken into to be stolen and they can't get it, and they rip out the dash then any destruction is generally called vandalism. Now if they get the started and out of the driveway it's theft. Different coverages by different things. Plus if the car runs for a second then won't restart they might think it's just a p.o.s.
 
Here's my 3/8" setup using a Carter hi-flow, filter, then Holley regulator set to 7 PSI. I had a problem when I first installed the Carter in that it was putting out 11 PSI (cold) and overwhelming the floats on the Demon 750 DP'r. Added the regulator and problem solved. Engine pulls hard all the way down the line to 6000 RPM so therefore electric not required. :burnout:

P6110001.JPG
 
One thing to remember is, when you bolt a pump to the block, it's like a heat magnet. The pump is as hot as the block is. When you bolt on a electric pump, you save a lot of heat being transfered to the fuel. Probably not a big deal for most, but it's fuel for thought!
 
Dave,what I would suggest is to redo the sending unit to 3/8 tubing,spend the extra cash on some 3/8 braided flex line(easier to screw to the frame with wiring clamps) and is also a insulator to heat and the cause of vapor lock.You run the mechanical fuel pump for either a 6pack small block,or a carter after market unit.make sure you run insulated line to the carb and clear fiters at the carb to check for fuel and dirt.If you wish you can have a regulator if you want,depending on the look you want,you may want a stock look.IF,at any time you see your self running out of fuel,you can install a inline electric pump at the back with little problems.I have even gone to the piont of running a gas cooler up front,in front of the rad and back into the engine bay to the carb.Think of some of this and email me back,Mrmopartech
 
Demon Seed. That is the look I am going for with the Aluminum lines. I went ahead and talked to Don at FBO today and I'm going with his carter hi-flow pump that has the cast housing ported and inlet/outlets ported to 3/8 NPT instead of the stock 1/4 NPT. He has never had one returned for warranty and has never blown the diaphram. His bench test flow rates for most units average 112 gmh and max 118 gmh.

The 1/4 NPT fitting on those pumps is total crap. Thats why they have a 50% fail rate and don't really flow at 120 like the advertising say. The originally carter pumps were 3/8 but people were cracking the housing by over tightening the inlet/outlet fittings. So carter decided to change to 1/4 npt to reduce the chance of over torque. Going from 3/8 to 1/4 increased the pressure and demand on the diaphram and the pump therefore fail more often. Same goes for the Holley pumps. Got this skinny from Don at FBO.

DemonSeed talk to Don at FBO and maybe he can port your pump and you may not need the regulator. Although it may be nice to have anyways.
 
I wouldn't waste my time running a mech pump. I keep it simple using a stock type 3/8 sending unit in my 63 and use the simple Holley red pump just like on my boys Dart. Has the regulation built in. No vapor lock to worry about with fuel coming from the tank under pressure and that red pump will work fine into the 10's as we still have the stock 5/16 line on my sons mid 11 Dart. Car can sit for months in the winter and then turn on the key and the pump runs and fills the carb bowls. Pump the gas pedal hit the key and she fires up. No cranking the eng waiting for mech pump to fill the carb bowls. Ron
 
daves66valiant said:
Demon Seed. That is the look I am going for with the Aluminum lines. I went ahead and talked to Don at FBO today and I'm going with his carter hi-flow pump that has the cast housing ported and inlet/outlets ported to 3/8 NPT instead of the stock 1/4 NPT. He has never had one returned for warranty and has never blown the diaphram. His bench test flow rates for most units average 112 gmh and max 118 gmh.

The 1/4 NPT fitting on those pumps is total crap. Thats why they have a 50% fail rate and don't really flow at 120 like the advertising say. The originally carter pumps were 3/8 but people were cracking the housing by over tightening the inlet/outlet fittings. So carter decided to change to 1/4 npt to reduce the chance of over torque. Going from 3/8 to 1/4 increased the pressure and demand on the diaphram and the pump therefore fail more often. Same goes for the Holley pumps. Got this skinny from Don at FBO.

DemonSeed talk to Don at FBO and maybe he can port your pump and you may not need the regulator. Although it may be nice to have anyways.
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Thanks but it's fine, it's already 3/8". A word of advise when screwing in the NPT fittings, use the teflon goop (swak) not teflon tape. The teflon tape adds to much stress to the hole and makes cracking the fitting that much easier.
 
demon seed said:
The teflon tape adds to much stress to the hole and makes cracking the fitting that much easier.
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And teflon tape is more likely to plug stuff up if a little tiny piece of it should somehow end up traveling thru the system, pain in the arse to get out of jets and idle cicuits, etc. Paste is much much better. One of the many jobs I do is replace fuel hoses and pump handles for several local convienance/gas stations and the new pump handles/breakaway fittings/hoses all come with big yellow tags warning NOT to use teflon tape for the same reason, to prevent plugging up some poor saps fuel system with chunks of that crap.
 
323775.jpg


I use the same regulator with a local gauge to set pressure. Line is 3/8 but I ran it along the stock route to keep it away from the headers. I'll get a better picture of how it dumps into the carb when I get home tonight. I have a Carter AFB 625, so I didn't need to fuss with a dual feed setup. In this pic you can't see my regulator mount bracket very well.
 
Mrmopartech said:
Dave,what I would suggest is to redo the sending unit to 3/8 tubing,spend the extra cash on some 3/8 braided flex line(easier to screw to the frame with wiring clamps) and is also a insulator to heat and the cause of vapor lock.You run the mechanical fuel pump for either a 6pack small block,or a carter after market unit.make sure you run insulated line to the carb and clear fiters at the carb to check for fuel and dirt.If you wish you can have a regulator if you want,depending on the look you want,you may want a stock look.IF,at any time you see your self running out of fuel,you can install a inline electric pump at the back with little problems.I have even gone to the piont of running a gas cooler up front,in front of the rad and back into the engine bay to the carb.Think of some of this and email me back,Mrmopartech
Click to expand...
The cool fuel is a cool thing
 
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