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Fuel Tank Vent/Valve
micklax - 17/4/12 at 06:05 PM

This might be a daft question so accept my apologies if it is!!

I have a 4.5gal MK alloy Fuel tank fitted to my Locost, which has two pipes at the top, I assume one being a return feed and the other to vent the tank. As I don't have a return from the Carb I need to use one or both of these pipes to vent the tank. The regs state that the venting of the tank must incorporate a non return valve.

My question is what type of non return valve do I need? Is it a straight forward valve as available on ebay etc, or does it need to be some sort of valve designed specifically for venting a fuel tank?

Once again sorry if this is a daft question!!!

IainL - 17/4/12 at 06:45 PM

I used one of these Link to Tank Vent and the other I blocked off, using a small length of hose and a bolt.

IainL

bassett - 17/4/12 at 06:52 PM

I bought the same as in the above link. works so much better than a few coiled loops of fuel pipe i tried first which still blew loads of fuel out. Think mine was from merlin motorsport though.
Adam

daniel mason - 17/4/12 at 06:54 PM

It needs to be a roll over valve really. With a ball bearing to stop fuel spilling out in case of a roll!
They vent he tank but block it when upside down

dickie b - 17/4/12 at 07:35 PM

I think this is an excellent question - well I would say that as I have been scratching my head over this one too ! ( exact same problem to solve on my Fury)

anyone suggest one these rol-over ball-bearing / vent valves as described in previous post? I dont know what I need to buy (though it sits on the end of the vent pipe, rather than in-line)

I am using an injected k-series rather than carbs though. Fuel cap is Newton, and non-vented.

cheers
Richard

IainL - 17/4/12 at 07:48 PM

I think the one I mentioned earlier can be used as roll over type as the spec quotes 50mbar blow off/5mbar vacuum

The quote below is from there spec sheet hope this helps

Ø8mm Vent, in-line with push-on ends, pressure relief 50mbar blow-off/5mbar vacuum (TF-AF-009)

Cheers
IainL

Mr C - 17/4/12 at 07:56 PM

Be carefull if fittng direct to the tank as I had a valve fitted directly to the tank using a welded in boss. There was a hole that ended up covered because of this and it wouldn't function properly. Just double check the installaton instructions most are designed to to inserted in the tank wall and fixed with a nut from the inside.

I knocked the guts out of mine and stuck a pipe on it (a very expensive connector!!) I've currently got a heap one way valve fitted but its not satisfatory as the tank builds pressure up, so have ordered one of these to sort once and for all.

fuel valve link

Dave Bailey - 17/4/12 at 08:59 PM

Think Automotive do a valve that will vent at pressure but will not allow fuel out...

Dave B

micklax - 17/4/12 at 09:22 PM

Crikey, I was expecting about a fiver, not forty odd quid!!!!

Tight Yorkshireman you see!!

Mr C - 17/4/12 at 09:30 PM

quote:
Originally posted by micklax
Crikey, I was expecting about a fiver, not forty odd quid!!!!

Tight Yorkshireman you see!!


If you find one cheaper let me know!! The cheaper valves only work one way unfortunately. CBS do this one for £25 which is the same as I had originally.

CBS fuel valve

big-vee-twin - 17/4/12 at 09:35 PM

I've just ordered this one link from demon tweaks.

I wrote to them and asked if it also acts as a roll over valve as well as a two way breather and they have confirmed yes, cheap at £10

micklax - 18/4/12 at 09:47 PM

Thats spot on thanks very much..

procomp - 21/4/12 at 06:14 PM

Hi

As discussed above when using a vent valve you need to make sure that it is a free flowing in both direction type. Most supplied are only a one way valve which can lead to a few problems such as the tank being sucked in and bellowed out. This can cause problems such as the tank being stressed around seam areas and splitting as very few tanks are sufficiently braced internally.
My personal view is that the ball bearing type are more reliable than the pressure type as the valve is only ever sealed when fuel escaping closes the valve leaving it free to breath freely at all other times.
I understand that the pressure one listed above is a low pressure type but always check by blowing through the valve with your mouth, ideally you should be able to open the valve by mouth. If you cant open it with by blowing through it in both directions it's best to avoid using it.

Cheers Matt

Stott - 17/5/12 at 08:39 PM

quote:
Originally posted by big-vee-twin
I've just ordered this one link from demon tweaks.

I wrote to them and asked if it also acts as a roll over valve as well as a two way breather and they have confirmed yes, cheap at £10



I know this is a thread from the dead so to speak but I thought I'd add to it for people who come across this in search results like I did.


Further to what big-vee-twin posted above, I rang ATL technical today and asked about the valve he linked to, they confirmed it is NOT pressure relief, it's vacuum and roll over only.

Sorry to dissapoint but I thought I'd share the info.

ATB
Stott

owelly - 17/5/12 at 11:08 PM

I've used an electric tank vent off a Corsa. It opens when the pumps running. I've also added a tee piece so I can fit a relief valve in case the tank tries to expand in hot weather!

Like this..


ETA piccy.

[Edited on 17/5/12 by owelly]