KJL

I run a carburetor and was wondering if there was a better alternative to using the old style mechanical push-rod style fuel pumps?

ezobens

For a naturally aspirated, carbureted engine, you can't beat the bullet proof simplicity and reliability of a mechanical fuel pump in a street car.

Now if you're all out drag racing with a mega-HP motor, the electric pump could be the better option-

No need to over complicate things if it's not required for your application.

76strokervette

For the power potential of your build you will need a race pump with a regulator and 1/2 inch fuel lines.Most likely it will be easier with the electric pump and fwiw is worth I agree with Tony on the carburetor.I would run the dominator.

KJL

I was leaning toward that myself but my builder felt strongly about it. Anyway.... 1/2 inch line from tank to pump as well? That sounds like another project.

KJL

Its no drag car but it may be capable of 675 HP.

C3 Stroker

Personally, I'd wait to see if I really needed an electric pump for your range of build. I use a mechanical 170 gph "nascar" Carter pump. This is the same pump branded as "superspeedway" by Barry Grant, and other manufacturers have also put their name on it and sell it as well. I got Carter's version because it is about 7psi and no regulator is needed. Through the stock fuel lines, I have never starved for gas on the most "bonzai" of 10 sec. runs. C3s do well on mech pumps thru 700 hp and, as I mentioned this one is good enough for NASCAR.

BTW, I agree with the Dominator for your application. Also, the May 2015 issue of Chevy High Performance magazine tests Shafiroff's 434 700hp......good reading, compare to your build.....theirs made 705 power, 600 tq.

KJL

Thanks for the information. I will give that a try with my stock lines first. I will give the 4150 a try. It is not an out of the box unit. Apparently they are custom built for specific application. I think my builder was just following my initial directive for streetable power. I guess there is a fuzzy line there regarding how a person interprets that. He typically builds engines for car and boat racing.

bluedawg

I agree 100%, there are formulas and the fuel pump companies that will direct you in the right way, a mechanical with a fuel regulator and tying into your return lines. You Might need to increase line size, but I wouldn't think so unless your reving into the higher rpms with larger cubic inches.

Super6

I run a 540 with a 110 gph Holley mechanical pump. Only had it up to 5500 so far. The "NASCAR" pump sounds to be plently. The near-stock mechanical system is so simple, why mess unless there's a need?

KJL

I found this thread info on another web site. Very interesting. It would appear that the pump is not the weak link in the system. Other info I found talks about friction losses using the 3/8" stock line as the ultimate limiting factor. No doubt a 1/2" line would be better than a 3/8" line. That said, it is likely big enough for my engine. I will likely go with a 8 or 9 psi mechanical pump and regulate it down to 7 psi and see how she does on the dyno.

I am having a hard time tracking down this NASCAR pump mentioned by C3 Stroker. Suummit has the Edelbrock 17000 pump that is rated at 170 gpm and 9 psi for 390.00.....damn. They are proud of that pump. There are other cheaper pumps that flow 170 gom but are rated at lower pressures. I think there is one for 7.5 and another for 8.0. From what I have read, using a smaller feed line from the tank, a higher rated supply pressure and regulate down to 7 psi would be the best approach.

[I]"A good mechanical pump is just fine for most folks. Consider the following:

Here's some data I've gathered up from 3 different 540's:

625hp Bill Mitchell 540, consumed fuel at a rate of 49 gal/hr at WFO throttle on the dyno. That works out to .47 lbs fuel/hp hr for its BSFC (Brake Specific Fuel Consumption), which is a fuel efficiency measurement. The lower the number, the more efficiently the engine is burning the fuel it is consuming.

722hp Beck Racing Engines 540, consumed 50.3 gal/hr, with a BSFC of .42 lbs fuel/hp hr

890hp buddy of mine's 540, consumed 56.7 gal/hr, with a BSFC or .38 lbs fuel/hp hr

This is a reasonable cross section of the very popular 540's. This group averages out to 746hp with an average fuel consumption rate of 52 gal/hr, where the average BSFC = .42 lbs fuel/hp hr, and keep in mind that these are real world actual numbers. You can use the number .5 lbs fuel/hp hr, if you are starting out with no baseline. So, this the amount of fuel these engines want, now let's look at what it takes to give them what they want.

Consider a tank with fuel 6" deep. If that tank has only a 3/8" hole in the bottom, it will gravity feed at a rate of 1.8 gal/min or 108 gal/hr. Which is more than double what those 540's want. At that rate, a 16 gal tank would run dry in about 8.9 minutes. But with a 750hp 540 sucking on that tank at a rate of only about 52 gal/hr, it would take about twice as long to empty the tank, which wouldn't run dry for about 18 minutes. Even considering factory 3/8" hardline frictional losses, the flow rate up at the engine is still WAY WAY more than that 540 could ever want. In addition to that, a 14 psi mechanical fuel pump, free flow rated at twice the engine's actual consumption rate, and regulated to 7 psi, can also feed all the fuel the 540 can drink and maintain plenty of pressure to deal with all the launch G-Forces that the 540 could generate in an average weight hotrod. Just using the factory 3/8 hardline and a good mechanical fuel pump, can provide about a 100% margin of safety in terms of fuel delivery.

Actually, one Camaro guy reported running low tens with a 14 psi mechanical fuel pump regulated to 7 psi, and free flow rated at 130 gph. He'd run it that way for a few years without issue, but all his buddies told him he needed to step up to a better fuel system. They told him that he couldn't possibly be flowing enough fuel, and that he'd go faster with a killer fuel system. They had no engineering data to back that up, but they all did it that way, so he should too. Peer pressure being what it is, he finally gave in and stepped up to a killer fuel system like all of them were running. After all that upgrading, he said his car didn't go one bit quicker. In fact he said he could tell no difference at all.

Now take a look back at those 3 engines above. All are the same displacement, but:

………..HP…………………………...............…gal/hr…………...……………….......……....BSFC lbs fuel/hp hr (fuel burn efficiency)
.
#1…….625………………………….......………….49…………………… ……….. ……...........47

#2…….722 (up 15.5%)………….…….....…...50.3 (up 2.7%)..…………….………..….....42 (improved by 10.6%)

#3…….890 (up by 42.4% over # 1)………….56.7 (up by 15.7% over # 1)……………...38 (improved by 19.1% over # 1)

You can see that it takes more fuel to make more hp. Afterall, only one things makes hp, and that's burning fuel. Everything gearheads/builders/racers do in the pursuit of more hp, is in support of burning more fuel and/or burning that fuel more efficiently. Some might find it interesting that, by looking at the BSFC, the engines get much more efficient as the hp goes up. That might be the opposite of what some people would expect, right off the tops of their heads. Even though the most powerful engine takes more absolute fuel to make that extra power, it only uses .38 lbs of fuel per hp hr, or 19.1% less to do that, than the weakest engine, which takes .47 lbs of fuel per hp hr, to make less power. Who says there is no free lunch?"

C3 Stroker

....KJL......Here is the fuel pump I have...don't know if still available...

http://www.speedwaymotors.com/Carter...-Pump,186.html

C3 Stroker

Found Carter pump available here....

http://performance-enterprises.com/v...gph-fuel-pump/



This is Holley's version, pricey.......

http://www.summitracing.com/parts/hl...make/chevrolet

bluedawg

If you do end up going mechanical, I found that the Holley, edelbrock and any other brand of fuel pump that can be turned to make the fuel lines clear the frame and point in the right direction are truly handy.

DO MA NEU!

BOOT77

The stock mech fuel pump for a 77 is 40 gph & will support 496hp. The 9.5psi spikes needs a reg @ 5psi on a holley. Still that's not drag racing.

KJL

Thanks for the info!

KJL

The Holley cost more because it is "Billet". Not exactly sure what you get for the extra 140.00 other than esthetics. I will likely run a reg regardless.

BOOT77

Sorry I wasn't clear, meant use a reg for the stock pump when using a holley type carb. Still you got it, aftermarket pump and reg is a good idea.

doorgunner

Rookie question: What is the best way to eliminate the extra-loud tap of the fuel pump pushrod on my 1970 350 cu.in project car engine? The current fuel pump appears to be about 10 years old but still has consistent 7psi pressure.

bluedawg

Have you pulled the pump and rod to see if the rod is worn?

DO MA NEU!

KJL

When I stripped down the engine to send to the builder, I couldn't get the push rod out. As it turns out it was mushroomed on the end and had to be filed down in order to remove. The spring in the fuel pump may be getting tired as well no longer keeping the rod in intimate contact with the cam. I would remove and replace pump and rod if it shows signs or wear.