Hi, I recommened a Carter 172GPH pump to a friend, he bought it, but the outlets are hitting the frame. Can you take out eh bolts and rotate the body to turn the pump so the outlets come out in a different orientation? Also when using a double pumper holley, do you need a regulator or is it set at 7PSI? thanks!

You can rotate inlet/outlet plate to your liking. No regulator needed. What is your friend doing with the -10 AN inlet and the -8 AN outlet?

Thomas

Cody, rotate as you want and no regulator is required.

Thomas, take a look at this pic.


http://www.boomspeed.com/mc71454/fuel6.JPG

Yes, you can turn it. It's better to keep the pressure at 7 psi when the car is running under load. Pressure drops off from idle so set it for the pressure you want when running. You probably do not need a regulator.

And IMO you need a big inlet line with a high volume mechical pump to get it to work right. My Carter is running 3/8 inlet and is starving the engine at higher RPMs so I'm reworking my system right now.

Eric, what is your fuel pressure at higher RPMs and what type of setup are you using? fuel log? stock lines? 5/16 or 3/8 pickup? fuel cell? filter type?

The setup in the pick ran 11.30's to 11.40's. with an 850 carb at 117 mph.

I used the same pump only feeding it with a -10 line from a sumped tank with a full tank of gas to 10.70's at 125 mph. Fuel pressure read 3 to 4 psi at the top end, but a comparison test between electric system at 7 psi and the Carter 172 at 3 psi was no different in ET or MPH.

11.31 at 121.8 is pretty impressive, but it doesn't seem like you are starving for fuel in upper RPMs

Cody, I drilled and tapped a new set of holes in between the existing screw holes to custom fit the angle of the inlet/outlet plate. Worked out real nice as I was able to line up the inlet with the fuel line exit hole in the frame.

Good Luck

Jeff
65 Chevelle
12.57 @ 114mph
461 ci BBC

Well, I observed my fuel pressure drop all the way down to 2 psi. 11.31's is OK but it will run faster than that -- right now its popping and spitting and still going 11.4's @ 119 with the Carter.

I am running 3/8" line all the way from the tank to the pump inlet. From the pump its all -8 line with high flow fittings.

I am switching to 1/2" line from the bottom of the tank into a 140 gph electric, then using my existing 3/8" line forward of the electric pump.

Hi, I'm new to the forum (1st post). I've been lurking a while, mostly to learn more about big block motors. You folks have an awful lot of expertise among yourselves. I don't have a Chevelle at the moment, but am finishing up an old truck project with a 454.
I have a question about fuel line size for a carburator. Since the thing that ultimately controls fuel flow into the carb is the tiny needle/seat, why such a large fuel line (say, 1/2 inch)?

Thanks,
Mike

Mike, I don't have an exact answer for you, but consider:
1) gravity and accleration, fuel weighs ~ 7.5 lbs per gallon.
2) having two .120 n/s restrictions that far up the fuel system is different than having that size restriction closer to the source.
3) inside diameter of fuel line feeding into fuel pump inlet has a huge effect on the volume capacity of the pump.

Thomas

to #3 above, even kinks in the line will cause a mechanical pump to starve out at higher rpms. I replaced a very serpentine section of hard line right above the tank and lost my fuel starvation problem at near 7000 rpm. Can certainly see how mech pumps like it very low restriction feeding into them. Especially under acceleration.

What I did on BigRed was, run the 1/2" line on top of the frame rail once it was in the motor compartment.
Then it steps way up to a 1" fuel hose about 18" in length. This large hose extends forward and above the fuel pump.
The idea is that the loop in the hose as it bends down and back to the pump acts as a psuedo fuel log momentarily pushing fuel back towards the pump on hard acceleration.

Thanks for the insight. One more question comes to mind, since the mechanical pump was mentioned: Since the mechanical pump sends fuel down the line in pulses (assuming it is at the point of starving the carb), it would seem that a bigger fuel line would be better/needed. Now, with an electric pump, could I get away with a smaller fuel line? In other words, would you consider a 3/8 line for electric pumps to be equivalent to a 1/2 for mechanical pumps?

Thanks

The Carter 172 is basically the same pump used in Nascar.
Those motors run 9500 RPM, supporting over 800 HP

No reg on my setup btw.