I removed the feed lines from the bottom of the fuel tank and on the larger diamater line there was a rubber seal , while there was not on on the smaller line. Are these necessary? Can they be purchased separately? If I was to make one, what material should I use?

Thanks in advance.

I replaced mine when I had the tank boiled and cleaned. I made them out of some type of chemical resistant gasket material. Seemed to work good.

Yes they are necessary. Your fittings will leak with out them. BTDT.
Its no fun having to pull the tank and do it right a second time. I went down to my hardware store and asked for some gasket material that could be used for gas. I got a 4" by 4" sheet for less then a buck.

Both the small and large lines should have a fiber washer. I believe they're still available from Porsche (try Pelican Parts). They were available when I R&R'ed my tank but the shipping was 5 times the cost of the washers ($1.00 for washers and $5 for shipping).

I ended up using some old brake disc caliper copper washers from an old Chevy truck I had. I just sanded them smooth on both sides. Been about 2 years and no leaks yet. In retrospect I should have bought the original washers and I wouldn't still be worrying about leaks.

I could never find any from any of the usual Porsche places. Ended up using some small copper crush washers.

BTW, I tried without the washers.....not so good.....leak city.

Good luck, of all the items I have purchased and replaced for my car....this was the most difficult to locate.....good times

I picked up some from zims a year or so ago.
Zims

--- bill