G'day,

Gotta plastic tank - added couple of galls to check if there was any of the dreaded reaction. So far, nowt. Tank remains leak-free. Any other checks I should carry out?

Now for the question :-
Tank was supplied by PTM (where he now??). There are 2 connections:-
A - outlet to fuel pump. So far so good.
B - outlet on top of tank. To what has this to be connected??
Have heard that tank has to be vented to inlet manifold. Is this correct???

Dick

Well

depending a bit on your configuration..

but normally you have an pump outlet..
and an return inlet to the tank

(that's the one on top)

then you maybe are in need to use an vent valve...

but i think you arent because the first cap that is 100% leak free i need to find..

and an tank valve is only in need if your pump sucks vacuum...

soow if you have carbs use the outlet

and nothing more..

TKS

You don't need to vent the the manifold, just to atmosphere.

Modern cars vent to the inlet manifold due to emmission requirements which don't allow hydrocarbon vapour emmissions! These vent periodically though, controlled by a solonoid controlled by the ECU, which opens to allow inlet vacuum to draw vapour in through a carbon particle filled canister, which I guess prevents any mishap with backfiring.

Fellas - Interesting feedback, thanks.

Re: Return flow: surely, this is for injected systems only?? Is rtn line necessary for carb type system??

Dave - It'll be the OE twin-choke Weber, which I think is DGAV (?).

One fuel line in mine for the twin chole DGAV plus a one way vent at the tank.

I just tapped a brass pipe fitting next to the outlet pipe and put a one way valve from thinkauto.com which i think was about £20.
Rescued attachment MK Indy build pics 162.jpg

one with the red one way valve on
Rescued attachment MK Indy build pics 054.jpg