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petrol twin Webber question

12 Feb 2016, 4:54pm
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:ear:
12 Feb 2016, 11:51pm
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.
13 Feb 2016, 12:17pm
On some applications a return line to the tank is required, mostly to stop fuel vaporisation ( eg where carb and exhaust are close together).
13 Feb 2016, 5:54pm
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 .
14 Feb 2016, 12:23pm
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.
14 Feb 2016, 12:29pm
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.