So to get a handle on this I actually bought from a junkyard 2 lock ring sections cut from old gas tanks. The first, a 72 B body I think, had an O RING. I didn't know those had o rings instead of flat seals. Can anyone confirm they have seen o-rings and what year model?

Also I'd be interested in the thickness of your old flat seal. Seems like they varied from .062 to .093".

Also can anyone confirm the thickness of the lock rings. Those obviously varied too. The 2 I have from a 72 and a 68 B body are both .050" but I know I've measured a .080" thick one before.

I'd Paypal a few $ for a picture and a measurement.

Thanks!

Never seen an O ring. The flat seal was used from 1957 to some models in 1978.Three part #'s ,1730096, 1948757 & 3404451 .Don't know the correct thickness for each one. The current repro lock rings that come with the majority of the senders are incorrect...not enough height so a thicker seal would be better.

Thicker seal isn't the problem it's the lock ring. The lock ring is to thin and bends.

I'll have to snap a picture the O ring style was from a 73 Charger.

And the 2 lock rings I have, 68 B body and 73 B body, are both around .050" thick and they are rusty originals.

What are those part numbers Nigel? The seal?

This seller claims NOS lock ring.

http://www.ebay.com/itm/142015687206?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I doubt that the ebay part is a NOS part.

This is what I came up with.
The lock ring and gasket on the left are the original factory parts from my 1969 Dart. The new lock ring and gasket on the right came with the reproduction Spectra Preminum fuel tank that I bought last year. I have measured and shown the thickness of the parts.

Great info rarefish. What year/model is that oem setup from?

Why do you say that? What leads you to believe they are not NOS??

1969 Dart GTS 340

Well for starters. If it was still in the factory packaging. I would believe it more, but if you look closer at how wide the gaps are on the outer edge of the ring and compare it to the gaps on the factory ring. You will see the ebay one is a lot like the aftermarket one in my picture. The OEM one has a 3/4" gap and the aftermarket one has a 2-3/16" gap.

And, when you figure that out then use a factory ring let's hope you've bought a good tank and it doesn't bent the tabs on the "new" tank...
I remember on one occasion going out for a build's maiden voyage pulling over for a quick inspection and seeing a drip at the sending unit...I crawled under there and just touched the sending unit and the lock ring popped loose from it's position !!! Talk about panic strength to reseat the whole mess along the road...I figured I was going to be a roast toasty when the gas hit the hot exhaust... That's the last time I've used the cheapy lock ring on anything...

The lock ring on Ebay http://www.ebay.com/itm/142015687206?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT these were available from dealers until fairly recently.

The large gaps in the lock ring are similar to the 73 Charger one I have. I'll post a picture of it and the gas tank section it locks into. Theres a new feature in the newer gas tanks (73 and up?) that wont allow you to use the older lock rings.

So I have a tank section and lock ring from a 68 B body and its .050" thick.

I'll have to pull the one from my own 71 Challenger and I may have to see if I can get a couple more like from a 62-65 B body.

If anyone is working on their car and has the gas tank out can you share a picture of the lock ring.

My 73 charger was untouched at the sending unit and it had a flat seal. I never seen a o ring type. I`m sure as stated the part number on the seal didn`t change until they went with the larger sending units in the later 70`s. Maybe your example was not the OE seal. I too had the same issue with the flimsy aftermarket lock ring. I dumped about 5 gallons of gas on my garage floor. What a mess.

Agreed these are NOS but later issue. Does anyone have a source for the correct 1969 style ring with the "shorter gaps"? I could use 3 of them NOS.

Vans sells a repro that appears do be a o ring for earlier cars http://www.ebay.com/itm/Mopar-57-58-59-F...W-/171225511370

AND it has the larger gaps. Maybe so it could be used on early Mopar AND on Ford that have the larger gaps.

Has anyone looked at the hardness of this repro stuff? If softer, the thinner dimensions are going to really make flex contribute to leaks.

So no one has a source for a NOS correct 1969 short gap lock ring? I guess I'll stay with my NOS later issue lock rings then. Reproduction parts are usually more of a get by part. Gas tanks are not where I want problems with inferior made parts. As to the hardness of the repop rings I would agree it may be suspect.