petrol twin Webber question

andysharrock · #1 12th February 2016, 15:54

would a twin Webber have a rerun to the tank , I got the new kit started today just to check it was a good engine . v6 3.1 ho yes
there is a return pipe from the carb with a bolt in leaking like a truper from the top of the carb, I dont see any reason for it other than a return is it ?. dont remember seeing a return pipe on the tank when I took it off it was a while ago

IanA · #2 12th February 2016, 22:51

The pump to carb pressure is not that high - 3psi -ish? The needle valve above the float shuts off the fuel. If there was a return, it would take the easy way back to the tank and starve the float chamber. What looks like a return could be used to feed another carb. Usually they are capped off but it sounds as if someone has used a bolt instead. Just needs a better washer or some Hermetite.

andysharrock · #3 12th February 2016, 22:54

cheers that makes sense

landmannnn · #4 13th February 2016, 11:17

On some applications a return line to the tank is required, mostly to stop fuel vaporisation ( eg where carb and exhaust are close together).

andysharrock · #5 13th February 2016, 16:54

I my try running the car with the fuel line blank removed and let it return to a petrol can just to test it... see if runs ok. I need a new tank anyway so if the new one has a return it could be put to use .

landmannnn · #6 14th February 2016, 11:23

You would need to put some kind of restriction on the return line to keep the pressure up, nothing high tech, perhaps just plug it and make a couple of of small holes in the tube above the plug.

y cymro · #7 14th February 2016, 11:29

Assuming you have a v6 Essex motor, you'll have a twin choke Weber carb (probably a 38DGAS), with two throttles opening simultaneously. It's not the same as 'twin Webers' which are things of wonder and great beauty.
If so, the carb will have a return feed to the fuel tank, for when the float valve is closed.
You will be able to test the carb by blocking the return, though it will be needed if you keep the OEM pump as they're prone to eating their diaphragms otherwise. Motorsport pumps, such as some Pacets won't need the return as they stop pumping once the preset line pressure is reached.