Weber return line

I am working on a return line from my Webers back to the tank. The main feed line is -6. Does it make any difference whether the return line is 5/16 or 1/4 inch. Thanks

Can I ask why?

Once you start doing returns you start looking at cross over valves etc and the whole system becomes a lot more complicated

Ian

Where I live it is very hot. I had problems with vapor lock on my cobra until I put on a retun line to keep the fuel moving.

Fair enough - re the evaporation - we had this problem out inn Zimbabwe too but never ended up putting in return lines. - Perhaps we were just lucky!

Well with the returns presumably you'll be using a Pollack Valve - so I believe you are restricted to 1/4 inch on the return (cannot remember for sure but it was smaller diameter than the feed side)

I would think that your regulator would be the "pinck point" on the system and thus the 1/4 should be more than sufficient for the return

Ian

fearsom said:

I am working on a return line from my Webers back to the tank. The main feed line is -6. Does it make any difference whether the return line is 5/16 or 1/4 inch. Thanks

Click to expand...

Hi, the return style carb set-ups I have been involved with use an electric pump capable of 20+ psi without an internal bypass and a return style reg such as the mallory 4309 to control pressure:

Mallory Ignition 4309 - Mallory Fuel Pressure Regulators - Overview - SummitRacing.com

http://static.summitracing.com/global/images/instructions/maa-4309.pdf

the reg is placed as near to the carb(s) as poss and the return line is the same size as the feed - for 400HP 3/8 inch both ways, 500HP+ generally 1/2 inch. I plumbed my carb'd blow thru turbo BBC in accordance with these instructions using 1/2 inch line both ways and a big EFI pump and never had any vapour lock issues even in hot start stop situations. Your return line needs to accomodate the full flow of the pump at the reg pressure setpoint while creating minimal backpressure at the reg return outlet.

Cheers, Andrew

Once you get your regulators and all set you will not have to add a the pollack valve and all the other stuff unless you feel a need for them. The economy method works just as well without them at all. What I am doing is the same as Dimi did with his fuel lines. The return line is T'd and one line goes to one tank and the other to the other tank. The same for the pickup lines and T'd to the fuel pump(external). At the bottom of the two tanks in the middle a right angle flange with connector line(5/16) is run between the two tanks. The area is small so use what will fit(aprox. 20 mm). This serves as a balance line to equalize the fuel level. A hole should be placed in the bottom of the frame for this line to run through to insure good level flow. If you then use a connector hose of several inches in diameter to connect the tanks at the top you can fill the tanks from one side or the other much like the old Lotus Esprit and some of the old GT 40 race cars. Then you will only need one fuel pump, one sender and one fuel guage. If you have diecided to use an in tank fuel pump you can eliminate the T'd pickup as the 5/16 line will feed the pump. Dimi has used this since building his 40 and has never had a problem. The attached drawing is the rear of the tanks. This was made for the DRB/GT40 Australia space frame cars. Yours may be different, but the setup is essentially the same.

Bill