I have seen as many tank neck styles/caps on Minis as the number of Minis.  Mine is a Canadian model, but not with a threaded type neck, (on either tank).  one tank has the lip cureled-in, the other is cureled-out, so taking two different style caps. both have leaked badly over the years and I have tried making various gaskets from cork and rubber with success over varying lengths of time, but they always eventually leak again.  I have considered welding on some modern screw-on pressure-cap/necks, but the black plastic caps are ugly, so I will probably just cut off the lips of the filler necks, and make up some alloy cap/plugs that slip inside the neck with Viton "O" ring seals.  Anyone else done this?  

Teflon makes very poor shims and gaskets because it tends to cold flow. Clamp it between two pieces of metal and it will slowly move out of the way, probably days or weeks, and the fasteners will lose torque. Ceramic coatings are good for blocking heat transfer as are titanium and nickel based alloys. In the gas cap application the pressure is relatively low so teflon works.

Kelley

Hey Doug, you ask me to measure something for you and I have failed to get that done. On the topic of teflon sheet, which we sort of are now. I purchased a sheet with the thought of cutting a gasket ( for lack of a better word ) to place between the disc and drive flange to reduce heat transfer to the wheel bearings and CVs. I also considered ceramic coating but have not tried either.

Steve (CTR) 

I have not posted to this thread yet but was contacted off-list about the fix I applied more than a decade ago.

I made replacement gas cap seals using sheets of regular (Buna-N) rubber and Teflon cut into donuts (2 from Buna, 2 from Teflon).  You stack them up (Buna-Teflon-Teflon-Buna) and use the stack to replace the single rubber/fiber/cork seal that was originally on the cap. The Teflon middle layers slip over each other like thrust bearings so the two Buna disks can get "squished" without distorting when the cap is tightened.  After 10+ years I have never had problems with gas leaking out under any condition.  Of course... the necks on my tanks were nice and flat without pitting or corrosion so the sealing surfaces are flat and continuous.

I believe I used something like 1/16" thick Buna and 0.010" thick Teflon.  The Buna-N and Teflon sheets (film really) are available at McMaster-Carr (mcmaster.com).

The bibs are not very popular here in the UK, you hardly see any of them on cars, they are more of a Japanese accessory.

Can't remember if I have one or two 8 gal fuel cells removed from race cars. One is a cross link poly and the other I think has a blatter.

Steve (CTR)

New gasket would be cheaper.

this one is kinda cute, but not sure how the leather will hold up...

 

Thanks for the insight everyone....may just bypass all this spillage and go for fuel cell.

Deb-

 

Correct, they are called "BIBS" -

BIG AL-

Following an accident in Canada in 1977 where a Mini spilled all its gas and caught fire."Canadian" spec Minis were sold with the screw in ugly cap , same as a chevy. No shiny chrome, but the neck on the 79 and 80 tanks is longer and has threads on the inside.They rusted and were ugly.

My Riley barely has a neck on the tank. The locking Gas cap is new and if you fill it more than 2/3 ; spirited cornering results in spills down the side of the left rear quarter panel.

If we plan to do a lot of cornering we don't fill the tank.

The gas neck bibs are very popular in the UK.

Deb

I wonder it that only happens to people named steve? When I came back I was not me any longer. Not sure what's going on but there are more and more of the old gang showing up.

Steve (CTR) 

I don't know if it will fit your cap.  I used a locking gas cap for mine.

it was one of many one off mods I have done to my car as I was building it and I only made one sorry.  sort of a trial and error process.

"What's with this "Mini25"? What, you got thrown off the board with your old ID....." Apparently so; I when I attempted to log in with my 11 year old password it wasn't accepted and I was forced to register as a new member. Apparently I've lost my identity, but that wasn't the first time; Someone's trying to tell me something.

Notabmw, will your baffle fit on any old style cap like mine?  If so do you have more?  I'd buy one from you!

Steve, you should have a batch made up, plenty of buyers here!!! The ones I got from SOMEWHERE are crap, and dont last at all.

LOL!!

Pick a response:

1) Yeah, right. You move up into it to take pics, so I owe you a windshield cleaning. Makes sense.

2) Touche. Maybe I'll clean your windshield when I see you on the 7th!

What's with this "Mini25"? What, you got thrown off the board with your old ID, or just using multiple ID's like your idol, OFB??

I filled both of my Monza cap vent holes with fuel resistant epoxy (the tanks already have a vent hose from both of them), and that combined with new thicker orange (soft durometer) silicone seals took care of the constant fuel leaking down the paint. 

You'd think the driver in front of me would have later offered to wash my windshield .... several times, just to properly clean it!

Yeah. It's a 'Monza' cap and I didn't click it fully. You'd think the cameraman would have let me know about it instead of dropping back, taking pics and telling me when we got there.

same with the clubby estate. the tank shape and neck angle doesnt help keeping the stuff in either.