as some of you may know i just got my 434ci scott shafiroff motor. it makes 576hp with a demon 950cfm carb with 7psi. i know that carbs don't require alot of fuel pressure(5-7psi). i have a holley high flow mechanical pump but im not sure that it will be enough to supply a 950 in the higher rpm. i did a search but i really could find anything that could answer this question. if i do need to get one could anyone recommend a good one. also i would need a regulator. i saw when i did a search that everyone seems to be a fan of the mallory 3 port. would that be a good regulator. thanks for any help.

 

my father motor is making around 525hp and is still using the BONE STOCK 305 mechanical pump. i'd think you'd be fine with that holley pump.

 

The mechanical fuel pump is more than likely good enough to supply the needed fuel to your new motor.
I am not familiar with this specific application so I must ask if your mech. pump system has a return line from the carb back to the tank?
I believe most mech pumps do not have the return line feature.
Also it is my understanding that most mech pumps have a built-in regulator/relief valve as to keep the correct pressure.
The advantages with a correct electric pump system would be not only proper fuel volumn and pressure throughout the rpm range and easier start-ups but cooler fuel delivery, cooler carb temp and virtual elimination of "vapor lock".
The ideal system layout(IMO) would be a good size line from the tank to a filter and then to the fuel pump. Line to the carb from the pump and then a step-down sized line (or same size line) returning to the tank with a regulator in the return line.
Sometimes the more fancier electric pumps now have built-in regulation or their own matched regulator.
Also make sure you have a good sized power and ground cables going to the electric pump and/or pump relay.
A very good idea is to incorporate an oil pressure cut-off switch into the system that in the event of an engine failure the fuel pump will be cut off should oil pressure drop to a critical level or (Knock on wood it never happens) any acident that the ignition is left on and engine stops the fuel pump is cut-off.
There are many ways to wire a circuit this way and many good sources. Should you not find any just ask and I will be more than happy to write out a diagram suggestion for you.
Good luck with that great motor!

 

Your just over the edge of what you can get out of a mechanical pump.

On the street you have to deal with heat. A mechanical pump
doesn't like heat. The inlet side of a mechanical pump is under vacuum all the way from the tank to the pump.
Heat + low pressure/ vacuum = fuel boiling.
When the fuel boils in the fuel lines it stops flowing.

A street car that stops and goes in traffic sees alot more heat on the fuel system than even a Nascar car does.

At your power level you pretty well need a electric pump mounted at the back that pressurizes the fuel line and pushes the fuel to the front of the car.

I would get a pump rated to 140 gal/ hr (freeflow) or more, use 1/2" fuel line including the pickup in the tank and use a hiflow regulator to trim the fuel pressure to 7-9 PSi at the carb.
there are specilized mechanical fuel plumps that will in themselves flow enough to feed you motor but the heatsoak puts a damper on their practicality on the street.

Two Carter #4594 electric pumps with twin 3/8" fuel lines from tank to carb will do it without a regulator.
They have a few things going for them on a street car.
low noise ( for an electric pump) , $$cheap$$, don;t need a regulator. Much more reliable than a holley blue pump.
Pretty simple.

 

http://www.racepumps.com/tech.html

All the pump you'll ever need.

Electric pumps put alot of heat into the fuel, especially when your not running a return style regulator. size of pump will also determine how much heat it transfers to the fuel.

anybody that drop the money and run 2 electric fuel pumps and 2 fuel systems needs to catch up and realize it's 2005, there are plenty of fuyel system set ups that easily support that kind of hp and not break a sweat or be unreliable.

Wires coming out of my A2000 were only 12ga. so come off a relay using 12ga. wiring for any pump and you will be fine, think the Holley pumps are 14ga.? pretty small stuff. My fuel got extrememly hot with the internally by-passed A2000 pump, if I were to do it again, it'd be with a return style regulator. Electrical pumps are noisey, even with return regulator, they're noisey.

 

is this one good. its rated at 140 and comes with a 3 way return regulator

http://store.summitracing.com/defaul....asp&x=20&y=13

 

That looks like a pretty good kit. Run some -8 or -10 for the system and you'll be good to go.

 

what size fuel line should i get for it

 

The faster a car is, the more likely the force of acceleration will impede the fuel flow from the tank to the motor. When you have a mechanical pump, it must suck the fuel from the tank against the force of acceleration to the motor - an 9 second car would starve to death, an 11 second one would have low fuel pressure. An electric pump located near the tank would only have to suck for a few feet - it pushes the fuel to the motor mechanically - a lot more reliable form of movement.

If your dad busted both nuts to buy a Shafiroff motor, why would he cahnce that investment on a mechanical pump? sounds like a big gamble to me.

 

I would recommend 1/2" line so your covered, 5/8" might be overkill, but you'd have the volume there if need be.

 

electric fuel pumps are annoying
and ive replaced mine 3 times in the past year and a half
120 bucks each time

 

IHI: Some things from the stone age just seem to keep on kicking the pants off the new "Hi tech" kid stuff.

By your won admission the A2000 didn;t work that well on the street. ( over heated fuel)
They were designed for drag racing.

Check the $price$ and compare to a pair of carter pumps @ $59 / each. No relays required , no 3 port or return regulator required. 140GAl/hr combined free flow.
These pumps were origionaly designed for "heavy duty" OEM application. (A 1950's era dump truck I think) They last and don't leak and don;t overheat the fuel or pull much amperage.
In a word, these Stone age pumps "work" on a high perf street machine. If the motor was under 475/500HP then 1 pump would do it. After you've fooled around and rebuilt and $replaced$ many many other "race" electric pumps, get a set of these.
They will all likely out-live the rest of your car.
An in the unlikely event of one crapping out on ya, you can get a new one at just about any auto parts store for about $60.

Some things just don't need improving.

 

It's tough for me walking the fine line between "practical" for the street use and bad azz enough to keep up at the track for consistency purposes as well as easy to work on/with and tune.

I knew that A2000 was waay more pump than I needed and NOT recommended for street use, but bought it with the intention of installing a 300 shot of juice so I only had to have 1 fuel pump on board, the A2000 was still more than enough pump for that and worked great for most of the summer-Aeromotive was actually impressed the pump lasted as long as it did under the circumstances I put it through.

I'm currently running the tried and true Holley pump (Red pump with Moroso high pressure spring-19psi) and it's doing just fine. The Holley's are proven in my neck of the woods with many street/strip cars having 5+ years with no troubles, downfall:when I install my nitrous I'll have to install another pump for the nitrous fuel solenoids.

Had every intention of buying the new mechanical pump http://www.racepumps.com/tech.html , but honestly as my business is growing at a great pace right now(overwhelmed actually), racing and car stuff gets further away from my priority's, cant retire with a car that runs fast or pay for bills/put food on the table. Need to focus on growing so I can afford better faster cars later In fact I'm going to the track this Sat....not to race, but bid turning their consession stand into showers/restrooms! Guess I can go out and watch if I ever get the time.

 

On the subject of fuel pumps..does anyone have any experience with the Carter electric #P4600HP?100 gph and 8 psi.What kinda NA horse should this be able to support?

 

I have that pump on my Camaro - 9 or 10 years and it's still going strong. I had to use a regulator to work with the q-jet (too much pressure).

 

Don't have a flow test on the Carter P4600 "Guzzler"
but I flowtested a P4594 rated at 72GPH (US)

here is my test results

Flow test for carter 7psi electric pump. *battery voltage 12.5 volts DC

free flow 58sec/1 IMP Gal. 62 GPH Imp 74 GPH US

.156 jet 68sec/1IMP gal. 53 GPH 63 GPH US 2.5 PSI * this is the equivelent flow area of two .110" holley needle and seats.

.119" jet 86 sec/1 IMP gal. 42 GPH 50 GPH US
4.5/5psi

.093" jet 97 sec/ 1 IMP gal. 37 GPH 44 GPH US 6.5psi


1 Imperial gal. = 1.201 US gal.

A cars fuel system should be able to pump 1 imperial gallon
in 42 sec for a 12 sec et
36 """"""""' 11 """"""
30""""""""" 10 """""""
24"""""""""" 9""""""""
18 """"""""" 8 """"""""
under 14 7 sec et

1 US gallon of water weighs 8.33LBS
1 US gallon of Gasoline weights 5.8 to 6.5 lbs depending on the specific gravity. .74 =6.16
1 US gal. of Ethanol weights 6.59lbs

Higher supply voltage will increase the pump output