Can someone explain to me how the roll over vent valve works? I understand how the valve itself works, but whats to stop the fuel going straight out the fuel neck instead?

The fuel cap has a seal so when it's closed there shouldn't be any significant leak past it even if inverted. Only way for air to get into the tank should be via the vent valve.

If you have a decent filler cap it should seal
the one way valve is to let air into the tank
Good luck


Tank breather & non return valve



try this £3.95 + P&P

ebay item 170984262812




[Edited on 21/7/13 by renetom]

There is a ball arrangement in the valve which act as float cutting the fuel if it is in contact with the valve. Under normal conditions the valve remains open to vent positive and negative pressure, working to a maximum pressure usually less than 1psi though if this is exceeded the holes are blocked and the valve will close.

Hope this helps

where is the best place to get one from

merlin do a nice anodised range. not cheap but

quote:

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Originally posted by daniel mason
merlin do a nice anodised range. not cheap but

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think automotive were the cheapest when I looked. Comprehensive range too.

do you know their web address i couldnot find it

quote:

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Originally posted by Trollyjack
do you know their web address i couldnot find it

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Cheap method (not sure about IVA)

Not sure about iva rules at the moment but i have used spare fuel hose and copper pipe no valve if the cars turns over the outlet is higher than the tank (but below it normal way up) if you work around the tank it is impossible for fuel to escape but you still have equal pressures regardless of whether the car is on its sides or upside down or normal way up.

Nick M

Sorry Fellas
Thought i was in IVA suppose you racers have to have vent valves.

Nick M