Can I use one of these as a roll over valve for my fuel tank
https://www.ebay.co.uk/itm/ALUMINIUM-NON-RETURN-CHECK-ONE-WAY-VALVE-ROLLOVER-BREATHER-FUEL-SYSTEM/162836920435?epid=1639988657&hash=item25e9d63873 :m:mhQvErCel4FlkIBLBwqRDpA

assume if I just mount it vertically with the arrow pointing downwards it would work?

[Edited on 26/2/18 by mikeb]

Hmm now I had one of these plumbed into my landys fuel line just in front of the carb in a bid to stop the fuel running back to the tank. Not actually the problem though. Anyway its just a metal plate, spring loaded and not a ball or anything that would care about which way round it was. I took mine out but apart from the question of how good the presumed O ring is it would probably be just fine. The arrow is just the flow direction. Got mine from autosave, for less than a tenner.

Not really as that's only a one way valve. You need a 2 way breather valve that allows air in and vapour out but stops fuel flow in the case of a roll over. Fuel vapour expansion is an issue not just due to heat but also caused by flow of fuel from return line. I've seen a tank bulging due to a one way valve.

I've used a Corsa breather valve on mine, wired into the same circuit as the fuel pump. That way it's open when I need it, in the event of a crash the inertia switch cuts it all out.

https://www.ebay.co.uk/itm/VAUXHALL-CORSA-C-1-0-1-2-FUEL-TANK-VENT-VALVE-INLET-MANIFOLD-VALE-2000-2006/401496672107?epid=1926294488&hash=item5d7b1 1076b:g:e1kAAOxylpNTVoB~

Brake servo one way valve, the fuel fumes rot most standard valves and these are pennies.

One of these?

This is the correct valve for the job.

My IVA man asked me about the roll over valve and wanted to make sure it wasn't a one-way valve.

the black part sits inside the tank and has a ball inside. It allows air to breathe in and out until it's turned upside down and the ball shuts the valve off

Fuel Roll Over Valve 8mm Fuel Oil Water

After having a couple of cheaper inline ones fail a bit the bullet and got one of these (last one on page)...
https://www.thinkauto.com/cgi-bin/sh000001.pl?WD=breather%20valve&PN=On_line_shop_Tank_breather_valves_268%2ehtml#aTRL7

Not cheap but still working.