Silverblade

Hey guys, wondering if you can help me with my fuel pump requirements.

I am finishing up a carbed 347 and I would like to go with a mechanical fuel pump.

The motor is around 10.5:1, it has trickflow TW 170 heads, comp 282 roller cam, RPM airgap intake, and Quickfuel Slayer 750 vacuum secondary carb. It is fully forged and balanced so I don't mind revving it up. I don't want to starve it at high RPM but I don't want to drown the floats either.

The other question is, at what point do I need a regulator? Not that I am leaning towards Holley by any means but they have a 110 gph without a regulator and a 130 in a kit with a regulator. I emailed Quickfuel and asked what sort of PSI their 750 slayer carb needs and they said 5.5-6.5 which sounds a little low but perhaps that is the general consensus on here too? I am guessing my best bet would be a higher GPH fuel pump to make sure it can keep up at high RPM but use it with a regulator to make sure I don't flood the engine on the low RPMs? In my research I find half of the people say a 110 is more than enough and it feeds old 429s and modern 600hp cars whereas other people say you need anywhere from 130-160 gph (including Quickfuel when I emailed them about their 110gph pump with their 750 carb and they said 155 GPH minimum). It is interesting that some say their motor never starves for fuel but others saying they stuck a fuel pressure gauge on their car and the fuel drops down to 2-3 PSI when they wind the motor out. Not that I care about squeezing every ounce of horsepower out of the car or shaving tenth-seconds off a 1/4 time but if I am going to buy one pump or the other, I would like to get a good set up from the start.

Thanks guys.m

barnett468

60 gph is more than enough.

you need a regulator on any pump that produces more than around 7.5 psi.

i would set the reg to 6.5 - 7.0

Gun Jam

I run the edelbrock 1715 10 psi 130gph

I did this for several reasons one being that I wanted to actually go out of my way to run a fuel pressure regulator. This is because I got tired of watching my fuel pressure gauge get slammed around do to the inherent nature of mechanical fuel pumps and the pulse they produce. Adding the FPR instantly eliminated the pulse and provides very consistent user set 6.25psi (use a good quality reg like the aeromotive)

The second reasons is the 130 gph will suffer less sag during WOT than a smaller fuel pump. Fuel pressure sag is still evident (this is due to many reasons one being the old fuel line from the tank to the fender on the 1966...I should upgrade this)

These two items together are a solid setup.

67mustang302

It's going to depend partly on what kind of pump you run and the environment. Mechanical is fine for carb'd engines, and pretty trouble free. If you switch to an electric, then you want to spend money or you'll just end up with a pump that has issues...plus they need to be mounted correctly. Internal vs external and how hot your environment is will change things up, some external electrics don't do too well in hot environments.

As for flow, the rule of thumb for calculating is you take approx. engine horsepower and divide by 2 to get lbs/hr needed for a n/a engine, then divide by 6.3 to find gallons and multiply that by 1.2 to give a 20% minimum safety margin. So assuming 450hp, you only need ~43gph with a safety margin, so yes...60gph is plenty.

However, depending on the pump type and placement, there are other factors that will push you into certain manufacturers and designs, which leaves you with more limited options (the pumps are usually larger).

Silverblade

Thanks guys, I appreciate your input.

Gunjam, can I ask what motor you are running for comparison sakes? I am leaning towards doing exactly what you have done. 130gph with the aeromotive regulator. When the tech at quickfuel mentioned a 155gph I looked on summitracing and see that they jump from 130 to 170 which is quite a jump. The 170 also runs 1/2" fuel lines (-8AN) and I'm concerned if I ran a 1/2" line from the tank I would get a bottleneck at the outlet on the tank and starve the pump. Not sure if there is kits to upgrade that outlet? I haven't come across any.

As for the elec pump. If I could find an in tank pump I would consider it but the only one I found was from NPD and it was high pressure for fuel injection. If there was a carb set up I would probably go that way.

Thanks again guys

Gun Jam

155gph is way over kill...The 130 is overkill the main reason I went that route was for the 10psi...The reduced pressure sag is a side effect...and all this really because I wanted very consistent fuel flow no more pulse..

I am running a qft 600Hr (double pumper) I am only producing 300rwhp at 6k

I would recommend against the electric setup if you plan to stick with carb.

For experiment sake I ran the fuel pressure up to max 10 psi to see what I could expect in the event of FPR failure. It actually appeared to remain seated and did not flood I drove the car easy and it was operational.

67mustang302

Aeromotive has good in tank setups, and you can use a regulator and/or PWM to get the low pressure needed. But, that will be an expensive setup, as you're installing an entire fuel system with return, and modifying or replacing the fuel tank if you go internal.

If you're never going EFI ever, then just use a mechanical pump, way cheaper and easier. The only advantage an electric has with a carb is the ability to prime and fill the bowl, and it's not really worth it for the cost (which done right, is a lot).

Silverblade

Thanks again guys, I will get the 130 with a regulator.

racer_dave

I run Carter 110gph @ 6.5psi feeding a 800cfm Demon carb on my racecar's 358 . I run -8 line from the fuel cell to the pump so there's plenty of volume to the pump. If you try to run smaller line, or use the stock fuel line its like sucking fuel through a soda straw vs garden hose. It won't matter what the pump can do because it'll never get enough fuel to reach the limit. Likewise, make sure the line from the pump to the carb is big enough as well. ALWAYS use a regulator.

I guess what I'm saying is to consider the 'system' not just the pump. I'm running less pump than others in this thread for a race engine turning 8400rpm at WOT, and full throttle off the corners. It's a lot more than a street car would ever need.

JMHO

67mustang302

I'm running the "small" Aeromotive A750 external inline, and at my delivery pressure (45psi) the flow is a bit over 70gph, which works out to enough fuel to feed 700hp n/a with a 20% safety margin.

So basically, in a n/a engine add a 0 to the gph flow rate and that tells you how much power you can support (ballpark). A 130gph pump will feed around 1,300hp. Or if you do the math, 130 x 6.3 = 819lbs/hr x 2 = 1,638hp x 0.8 = 1,310hp with a 20% safety margin at 0.5 BSFC. Which is massive overkill for a n/a street 347 that probably makes 1/3 that power.