Hi guys,

Fitting a alloy fuel tank in the back of my car and will be fitting a fuel filler neck and cap through the lexan window,

Just wondering if I need to fit one of the one way breather valves or not because there is extra room because of the filler neck.

Any help appreciated.

Cheers

The tank must be able to breath two ways unless your planning on fitting a pressure vessel! The simplest solution is a piece of hose connecting to the top of the tank and exiting below the lowest point of the tank (so the fuel can't fall out if you end up inverted). The 340 essentially uses a glorified version of this solution with an extra tank to catch vapour in, there are no fancy valves if my memory serves me right.

Alternatively I believe there are some expensive snazzy valves on the market for the purpose that allow air to flow both ways but block fuel. If you're going to put the vent at window height be certain it'll do its job retaining the fuel if you end up on your roof! If you're going to do any form of motorsport check the rules as it is normally specified that the breather must be below the tank.