Carter 4070 electric fuel pump

[Pdxguy]

Based on multiple threads here the Carter P4070 electric fuel pump is being used successfully by lots of folks with dual Weber 40s. Question about the pressure. Looks like ideal pressure is 3-3.5psi for the Weber 40 dual carb set up. If I am understanding things correctly, the Carter 4070 produces 4-8 psi; above the recommended pressure. Am I mistaken?

Found this Carter marine unit, specified as 4psi, rather than the 4-8psi. Would this be a better choice? Any downsides to a marine unit vs auto specific?

https://www.summitracing.com/parts/crt-p4389

 

I plan on using a pressure regulator which decreases the pressure, meaning the flow velocity increases, ie higher volume per unit time. Not completely understanding carb needle/jet functioning, is the PSI (pressure) or GPH (flow velocity/volume) the problem when too high?

 

Last question, is the recommended psi based on what is delivered at a certain RPM, or from idle to full throttle?

 

I see a carburetor for idiots book in my future. 

 

Thanks,

Dennis

[Steven Hage]

I've got a 4070 pump and a Holley adjustable pressure regulator and a gauge and I've got it set to 2 psi and everything is fine so far

[TobyB]

PSI is the problem.

 

The Weber uses a relatively large needle in the float valve, and 

any pressure against it will cause it to overfuel.  But only at low volumes.

 

So you'll get high float levels at idle when you don't want that,

and low float levels at full load, when you don't want that.

 

I have yet to find an electric pump that DOESN'T overfuel a Weber.

 

I use a Mallory bypass- style regulator, which is slight overkill, but I

just NEVER have trouble with it, so why break that?

 

t

2 psi is plenty.  1 psi is enough.  As long as the flow is there!

 

[Dudeland]

I have that exact setup you are looking for in a box.  I took it off my car when I went to EFI.  If you are interested please PM me.  i will let if go very reasonably. It worked very well and only had non-ethanol fuel put through it. 

 

I also have the carb to go with it.   

 

P.S i can send pics.

 

 

[Pdxguy]

12 minutes ago, TobyB said:

PSI is the problem.

 

The Weber uses a relatively large needle in the float valve, and 

any pressure against it will cause it to overfuel.  But only at low volumes.

 

So you'll get high float levels at idle when you don't want that,

and low float levels at full load, when you don't want that.

 

I have yet to find an electric pump that DOESN'T overfuel a Weber.

 

I use a Mallory bypass- style regulator, which is slight overkill, but I

just NEVER have trouble with it, so why break that?

 

t

2 psi is plenty.  1 psi is enough.  As long as the flow is there!

 

What size return line do you use? Bigger than the feeder line or same size?

 

Thanks,

Dennis

[TobyB]

Same size, because I was lazy!

 

It has a gauge on it, tho, and it's stable enough.

The big thing is that it doesn't spike or creep up.

 

t

 

[Pdxguy]

What are the applications for three vs four port regulators?

[Stevenc22]

I run the 4070 with no pressure regulator. If you believe Top End Performance, Webers like 4psi and they recommend and sell the 4070 without any regulator.

 

https://www.racetep.com/manufacturer/carbs-and-injection/weber/electric-fuel-pumps.html

[Hans]

Hmmm. All know is my twin 40 set up isnt happy over 3ish. Both Italian and Spanish.

Edited June 29, 2021 by Hans

[John76]

3 hours ago, Stevenc22 said:

If you believe Top End Performance, Webers like 4psi

Stevenc22,

My day is ruined!

According to Top End Performance, EVERYTHING I have done with my Weber 32/36 is WRONG.

Have I just become content with VW Bug performance all these years?

Can't wait to find what potential lies within my hobbled '02.

John

[visionaut]

11 hours ago, Stevenc22 said:

I run the 4070 with no pressure regulator. If you believe Top End Performance, Webers like 4psi and they recommend and sell the 4070 without any regulator.

 

https://www.racetep.com/manufacturer/carbs-and-injection/weber/electric-fuel-pumps.html

FWIW, I ran my 4070 without a regulator for a long while, following TEPs recommendation.

I’ve eventually added a Powerflow 2-4psi fuel regulator (set to 2.5) after observing the 4070 output on my fuel pressure gauge. The regulator keeps the pressure much more steady.

 

Tom

[Clevis Woodruff]

My son's '75 daily driver has an unregulated 4070 feeding a 38/38.  He's been driving it for more than two years without any fuel-related issues, whether around town or at extended "highway speed" which is about 60mph with the 3hp12 transmission.

 

[Pdxguy]

Thanks all, appreciate the input.

 

Dennis

[Stevenola]

On 6/28/2021 at 4:49 PM, Steven Hage said:

I've got a 4070 pump and a Holley adjustable pressure regulator and a gauge and I've got it set to 2 psi and everything is fine so far

 

Ditto

[Dudeland]

Dude I am on hold.  I can't access my parts, due to the fact that I am storing a motorized wheelchair in my garage.   A long story, but I can't access my attic for 2 weeks.  If you can wait, then great, if not I understand.