T: Fuel Tank Petrol taps

Simon Dinsdale

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VOC Member
VOC Forum Moderator
I've been using taps from Screwfix for several years without any problems. From memory, they are around £6.00 and don't seem to have any leaking problems. They are sold for washing machine/central heating, etc.
This is what I use.

The 8mm description is the pipe o/d and is withing a couple of throu of 5/16". Discard the nuts and olives and the thread on the body is 1/4 BSP and fits straight into the fuel tank and straight onto the std Vincent fuel pipes. I also remove the yellow plastic tab off the lever. Another thing I do is thread the tank end of the tap body internally and fit a fuel filter which is available from several places:

Simon
 

BigEd

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VOC Forum Moderator
This is what I use.

The 8mm description is the pipe o/d and is withing a couple of throu of 5/16". Discard the nuts and olives and the thread on the body is 1/4 BSP and fits straight into the fuel tank and straight onto the std Vincent fuel pipes. I also remove the yellow plastic tab off the lever. Another thing I do is thread the tank end of the tap body internally and fit a fuel filter which is available from several places:

Simon
That's the one. Thanks for the tip about the filters, I've ordered two. I've got two external filters fitted but they do make routing the hose more difficult.
 

robin

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VOC Member
1/4BSPP mini ball valves are available from any hydraulic hose supplier' Normally male one end and female the other end plus a male/male union nut (these come in 2 sizes-small hexagon or large hexagon. Buy the largest bore size for 1/4"BSPP and the large hexagon union adaptor. To further improve sealing -use Dowty seals.
 

oexing

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VOC Member
Any seals exposed to modern fuel have to be Viton, teflon or cork, no NBR will do. So when going for o-rings or fuel tap seals you will choose viton or cork. Alcohol is NOT the point but all these thinners in the fuel like acetone, toluol, butane . So you could decide on the all brass taper type taps or modify the plain gasket taps like below in links for cork seals, rubber will not do. Auto fuel does not lubricate the rubber seal so operation is not smooth. I had best success with home made cork seals in the plain gasket types but then apart from the fiddling with delicate corks sanding them flat and drilling four holes to suit the tap housing you will be exposed to several bottles of red wine till you got a suitable collection of corks for that job - ah well, so be it . . . .
The all-brass taper type tabs will not work in the long run as like materials, brass on brass , cone-in-case , will lead to seizures and f***ed-up faces on the tapers and consequent leaks. So you´d copy the taper in stainless and lap that in the case for a permanent solution.
The ball valve taps should have teflon seals so great for modern fuels but I would not accept them on my classics for ruining the looks.

Vic

fuel tap 1/4

tap 1/4 "

circlip tap 1/4
 

mercurycrest

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VOC Member
Any seals exposed to modern fuel have to be Viton, teflon or cork, no NBR will do. So when going for o-rings or fuel tap seals you will choose viton or cork. Alcohol is NOT the point but all these thinners in the fuel like acetone, toluol, butane . So you could decide on the all brass taper type taps or modify the plain gasket taps like below in links for cork seals, rubber will not do. Auto fuel does not lubricate the rubber seal so operation is not smooth. I had best success with home made cork seals in the plain gasket types but then apart from the fiddling with delicate corks sanding them flat and drilling four holes to suit the tap housing you will be exposed to several bottles of red wine till you got a suitable collection of corks for that job - ah well, so be it . . . .
The all-brass taper type tabs will not work in the long run as like materials, brass on brass , cone-in-case , will lead to seizures and f***ed-up faces on the tapers and consequent leaks. So you´d copy the taper in stainless and lap that in the case for a permanent solution.
The ball valve taps should have teflon seals so great for modern fuels but I would not accept them on my classics for ruining the looks.

Vic

fuel tap 1/4

tap 1/4 "

circlip tap 1/4

I just push the brass petcock's tapered valve lightly, in from the spring side and twist it back and forth a couple of times and it unsticks. Been using them for donkey's ages with no gauling.
 

Texas John

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Non-VOC Member
Mercurycrest - thanks for your post which gave me the idea on how o free them up. I managed to get the petcocks out of my '48 Rapide this weekend. I soaked them in lacquer thinner for an hour, still did not want to turn. Tapped the spring side of the valve a couple of times with a plastic mallet and each one came loose and now they turn fairly nicely. I will disassemble and thoroughly clean them and then lube them with EZ Turn Fuel Lube when it arrives (suggestion from davidd (David Dunfey)) in another post. I could have used that stuff when rebuilding the fuel valve on my Model A Ford! Seems the stuff is popular with the antique car people, too.
 

LoneStar

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VOC Member
I've had good luck with the standard petcocks and these Viton O-rings instead of corks:


As supplied, the O-rings stick and make it very hard to move the plunger - but with the OD sanded down a bit, they're fine.
 
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