I lost the tear down pics so i have no images of how it came apart.

Can someone help me with the way to seal the outlet / return pipe that screw onto the bottom of the tank.

I have aluminium washers and fibre washers. I've tried with both, the fibres leak badly. They were squashed between the tank and the round collar fixed to the small steel pipe tail.

I've tried using just an aluminium washer in the same position as above but still a slight leak.

As the retaining nuts are a soft alloy i can't tighten them anymore.

Just in case i do ruin them trying to seal them, does anyone know the correct thread size of the outlets on the tank?

Auto Atlanta:

https://www.ebay.com/i/231867072992?chn=ps&fl=a

I've used this too.

https://henrichinc.com/shop/gasoila-soft-se...IhoC49UQAvD_BwE

I believe both go on each outlet, not one or the other. So tank>fiber washer>aluminum washer>tank nipple.

Others can correct me if I’m wrong.

Also, you may want to download the PET on your computer. Go to Porsche’s website. Classic area. It’s the parts list with exploded diagrams of the car. Extremely useful.

Good info above. thanks for posting

The catalogue shows outlet has 1 aluminium washer

The return shows 1 fibre washer only so i'm not confident this is correct. I think as detailed above is correct even though one is m10 & one is m8.

Ideally i would like to fit something like a copper pipe/union, maybe from something like a rally parts provider or similar but i need to know the thread size.

both washers should be copper, the AA versions are a bit small but they do work with the correct "crush".

Harbor Freight has a collection of copper washers, pretty cheap.
You could heat them cherry red, let them cool and they will crush very nicely like the exhaust head gaskets.

Like mgphoto just said both are copper.

Click to view attachment

The filter sock does have an aluminum base.

I do this as a public service every year. To anneal copper you heat to a dull red, or cherry red if you have the nerve, then quench in cold water. Not the same as steel. If you can afford solid gold or silver it is the same. Air cooling these metals can be used as a hardening technique.

I did this with harbor freight copper washers. Worked great. Now I'm running AN fittings. But I always anneal my copper...

I have never seen a copper washer used originally on a 914 tank. They are fiber. Not to say that is the best material. The ones I have found are hard and not a good fit. I made my own fiber washers out of gasket material. I use washers on top and bottom of the flange on the nipple. On the feed line the filter sock aluminum washer is part of the filter.
What is important is to hone flat the sealing surface on the tank. Did an install on a tank that would not stop dripping until we removed it, honed the sealing surface with a a piece o f wet or dry 240 grit on a flat steel lock.
Copper should work fine if annealed. It is harder than aluminum and may tk more pressure to seal. The aluminum nuts are fragile. I am hesitant to apply too much torque in fear of stripping the threads.
That whole original set up is a bit of a CF ( cluster fornication ). I found you and internally tap the threaded nipples to 1/4 NPT and install threaded nipples allowing use of lines that can be disconnect easily without removing hose clamps. I plan to go with AN-6 fittings to eliminate and sealing washers. This does require an external filter as the internal sock will no longer fit. My thought is get the crud out of the tank and change the filter rather than trap it in the tank. Ideally I want a threaded connection from the gas tank line to the tunnel lines. This would allow removal of a line to drain the tank. Maybe a Swagelok fitting on a SS line will work. Have to install it after the line is installed as the fitting will not go through the rubber block.

I used an aluminium washer above and below the collar on the 2 tail pipes. Put as much force as I dared to use and no more leaking pipes. Needless to say a quick spin around the block to test and all is good.

Rotary914 sells the fiber washers. Found in the member vendor sub-forum.

I used fibre washers and had no leaks straight off,if you can't get a seal with any type of washer add a little Hylomar universal blue that will complete the seal ....only product I have used that is truly fuel resistant,great stuff.

Thanks for the tip. Never Heard of it before.

HYLOMAR Universal blue gasket sealer is the leading non-setting gasket and sealing compound in use worldwide. It is used by many of the world's major automotive manufacturers and by several Formula 1 teams. It is non-hardening and non-setting, vibration resistant, seals surface imperfections and withstands rapid variations in temperature. Allows metal-to-metal contact and is resistant to combustion products, water, engine coolant, petroleum, lubricating oils, kerosene and fluorocarbon refrigerants. Dresses gaskets, threads and seals gaps up to .25mm.

https://www.google.com/search?q=Hylomar+&am...ent=firefox-b-1

I have used his washers and they are like original and ok at best. I want a better seal.
I found some SS washers with silicone rubber bonded to one side. Cant find both the large and small hole with correct OD. nee 8 x 16 and 10 x 16.

Bruce, did Robert's washers leak?

The tank leaked with his washers more because the small narro sealing surface n the tank nipples was not flat and clean enough. We had to remove the tank after trying several sealing methods. Honed the surface flat and carefully installed new seals.
Need full size 16 OD and 8mm & 10mm ID. I do not like having two sizes. No need to. Looking at a better more simple system. so far the internal pipe thread does away with all washers but eliminate the internal sock,

Thanks, hope this info is help with those who have difficult sealing jobs,I was a Loctite guy for decades,the Hylomar has proved a better product for many applications that the Loctite doesn't cover .

I've used Rotary914's gaskets and screens on three different cars without a hitch. Kevin already touched on the key. True and mated surfaces.

Does anyone know the size of the two union nuts? Before I pull the tank, could they be 22mm?

**Edit Yes, they are 22mm.