return pipe

bones · Post by **bones** » Sun Oct 04, 2009 9:31 am

Hi all, what size should the fuel return pipe be, main feed is 3/8, can the retun pipe be 5/16 or a 1/4" i/d.

rich

Ian Anderson · Post by **Ian Anderson** » Sun Oct 04, 2009 4:28 pm

Should be the same size as the flow

At Idle almost all of the fuel will be returning to the tank
By reducing the pipe size you may accidentally increase the pressure in the system above what the regualtor is trying to set

Cheers
Ian

mgbv8 · Post by **mgbv8** » Sun Oct 04, 2009 6:39 pm

Is this for a carb setup Rich ?

bones · Post by **bones** » Sun Oct 04, 2009 7:02 pm

yes a carb set up, its on my brothers motor, a holley 600 d/p,

rich

mgbv8 · Post by **mgbv8** » Sun Oct 04, 2009 7:32 pm

You need to think about the delivery pressure required Rich!!

And how much the pump can flow as well.

If the return line is too big, you will have low pressure at the carb.

Does the pump have a regulator fitted to keep pressure down to the right level ??

The Holley wants about 5-6 psi doesnt it??

I would think about fitting a Tee just before the carb, and fitting a restrictor in the return line.

I had this issue on my nitrous fuel system. The regulator did not like being dead headed. And it gave me fluctuating fuel pressure off the line. I put a plastic fuel Tee in just before the solenoids and found an old carb jet with a 2mm hole that fitted just right into the plastic Tee. I also fitted a glass fuel filter in the return line so I could see what was happening. The 2mm hole is enough to get a good flow back to the tank so the regulator can control properly. And my fuel pressure during a run is stable now.

Pel

topcatcustom · Post by **topcatcustom** » Sun Oct 04, 2009 7:39 pm

Do you need a return on a carb or is it because you are running a mech pump?

mgbv8 · Post by **mgbv8** » Sun Oct 04, 2009 7:53 pm

Depends on what fuel pump you are running Tom. If you use a high pressure pump via a regulator. A return line is a good idea to stop the regulator getting stroppy.

stevieturbo · Post by **stevieturbo** » Sun Oct 04, 2009 8:04 pm

More than likely the 5/16" return will be fine. I wouldnt drop as low as 1/4, although a lot depends on pump flow

bones · Post by **bones** » Sun Oct 04, 2009 9:37 pm

its an electric fuel pump, 140gph i think, hes got a nos fogger direct port system fitted ,and regulator, so 5/16 return will be ok then??

stevieturbo · Post by **stevieturbo** » Sun Oct 04, 2009 9:46 pm

140gph is a hell of a lot. Id sooner use a 5/16 feed and 3/8 return

bones · Post by **bones** » Sun Oct 04, 2009 10:03 pm

the pump could be the 125gph it flows 110gph at 7psi, the engine is a 360 mopar 420bhp, the pump has got 3/8 ports.

rich

stevieturbo · Post by **stevieturbo** » Sun Oct 04, 2009 10:04 pm

then just use 3/8 feed and return

bones · Post by **bones** » Sun Oct 04, 2009 10:30 pm

Ok thanks for the replies, i will let him know.

rich