fuel pump for Webers

[gumba]

I want to change from a non recirculating fuel system to a recirculating one for my 46mm Webers. I'm currently using a Carter 4070 pump with a 72 gph@6 psi. Will this work in a recirculating system, or do I need to go to a higher gph fuel pump. If I need to go bigger would the Carter 100 gph@8psi work? I currently have the pressure set at 4.5 psi.

3.4 twin plug w/46mm Webers.

[81 911 SC]

I've got a stock SC 3.0 and am using the stock SC fuel pump for my 40 MM PMO carbs.

[gumba]

I would like to stick with the Carter since it's already set up. Any idea what the SC fuel pump flows?

[jabb]

Originally posted by 81 911 SC
I've got a stock SC 3.0 and am using the stock SC fuel pump for my 40 MM PMO carbs.

Webers only like 3-5 Ibs of pressure I am sure PMO's are in that range also. Are you controlling the pressure with a Fuel Regulator ?

[81 911 SC]

yes I have an FPR

[bede]

The Carter 4070 will work fine with a recurlating system, if you want piece of mind put a restrictor in the return line

[gumba]

Thanks, I was planning on putting the restrictor in. Didn't know if the Carter flowed enough.

[A Quiet Boom]

Why if I might ask do you want to go with a recirculating system? The only reason I can think of is to keep the pump cool and possible stablize the fuel pressure but this typically comes at the expense of heating the gas in the tank.

I had a HUGE Essex pump on my drag car, ran a recirc for the street. -10AN feed lines with -6AN return, it would heat the entire tank in a 1/2 hour of freeway driving. At the strip I would close of the return and the pressure stayed dead level even with the force of a 10 second launch on slicks, wheel up. My pump had to be recirced for continuos use, hence the return on the street.

[gumba]

I was told it would provide even fuel pressure to both bowls in ea. carb and keep the fuel cooler.

[A Quiet Boom]

Originally posted by gumba
I was told it would provide even fuel pressure to both bowls in ea. carb and keep the fuel cooler.

Pressure will be equal no matter what, delivery is another issue. A good distribution system goes a long way here. I made fuel inlet rails for my Zeniths, crude first attempts but they work. They're fed by braided AN line from each side of my Holley low pressure regulator.

How does circulating fuel past a warm engine and transmission keep it cool? Unless it's being heated by stalling in the pump. A temporary temp sender in one of the carb fuel lines might tell a lot, especially if paired with one before the pump.

[gumba]

Not much help, I'm repeating what I heard.
In a non recirculating system the fuel is sitting in the lines in a hot engine compartment vs a recirculating system where it stays cooler because the unused fuel is being recirculated to the tank. As far as even fuel pressure, one bowl is supplying one throat and the other bowl is supplying two throats. So the first bowl gets filled before the second one. Now as to how much actual impact this has on things, I don't know. Maybe someone else will pipe in and can explain it better.
In my current system I use a Carter pump > Holley f/p/r set to 4 psi >pressure gauge w/2 outlets, one to ea carb. I also have a filter on ea. line between the gauge & carb.
The recirculating system was suggested in helping to keep even constant pressure and the fuel cooler.
'75 Carrera RS look, 3.4 twin plug & 46mm Webers.