[xk] Fuel Tank Detail

Thank you very much, Rob. This will get me moving forward for now. So, when the four ends of the tray are tightened up, the top of the tank presses against the curved cross member in the front and the two curved tabs in the rear, correct? Also, would you say that the holes that are in the channels of the new tray are about where the studs should go? Thanks.


Don’t forget the 11 pieces of about 1/2 inch thick felt that isolate the tank from the chassis and the floor. Rob gave you the dimensions of them above. Here’s a couple of pictures showing how they are installed. The tank pictures are extracted from a series published on Google by@Tadek :
XK120 Disassembly - Google Photos

Good luck with your project.

Roger Payne will chime-in if I’m wrong about this. There were two special British 5/16 nuts securing the fuel tank on the four hanging studs. The primary is the NN.131/L, which is a fine thread nut chamfered on one side and un-chamfered on the other side.

The second nut is the NN.231/L, a thinner “jam nut” which is also chamfered on only one side.

Probably correct, photo from Tadek. Why only 6 of the NN.231?

Mike, if I remember correctly, two of the upper NN.131/L nuts were welded to the studs/rods. So those didn’t get the thin NN.231/L jam nuts.

Bernard and all, thank you so much for this information; much appreciate it.

My wife makes weekly visits to the local fabric shops, so I’ll ask her to get the black felt. But, could you please tell me the actual thickness? One-half inch seems awfully thick. Thank you again.


I’m not 100% sure the felt used for the tank was 1/2 inch, it could be 3/8 but it’s pretty consistent. Also, the original felt was like a dark beige color and on one side and had a black thin rubberized coating on the other side. In any case, whatever felt you use, it will compress and keep the tank in place when you tighten the bottom nuts of the tank tray. Finally, I measured the length of the rods. The long ones are 12 and 3/4 inch and the short ones 8 and 1/4 inch.

I just got a box full of fuel related things from Moss, including the fuel tank felt kit. What I found in the box was self-adhering strips of black felt no thicker than 1/16". Be aware, it’s not the right thing.




Try finding “impregnated” felt (preferably using natural fibers like wool), which is resistant against water and “unexpected biological life in your felt”. I found good felt and cut it to size. This was “natural” coloured felt (and not black as many suppliers recommended) but when looking for information in all the “well-known” books, I see a number of pics with “natural” felt instead of black.

Bob K.

Thanks Bob. I got some 1/4"gray felt today. It should do it.



I did a little research on the subject :
Woolies in the UK seems to have the correct material :

So does Martrim, also in the UK


rolls of black felt will be available.
The black felt will be some sort of natural fiber.
I noticed the 20 or so rolls of narrower felts purchased from Woolies a year or so ago where probably made of nylons they were black but clearly the were nothing like the old natural products when cars first built.

Yep, that’s the stuff. There’s lots of that jute in my Mark V.

Thanks Bernard. I got my hands on 1/4 inch black felt from the upholsterer. It is a very tough and dense material. I asked him about the carpet underlay “jute”. He said that is really not the same thing. It’s quite a bit less substantial and less dense. But I don’t see why it couldn’t be a good substitute if one was unable to find the thick felt. Thanks.


I believe there’s a lot of that stuff on every Jaguar of this era. It’s actually nice to use as it doesn’t go out of shape as easily as the plain one without the black stuff. I think it might be also what’s used under the carpets (BD6468, BD6469, BD6470 & BD6471) based on the following picture of an original car

photos provided by Mike May @XK-SS

I think in the end, one uses what’s available or what’s on hand, provided it’s thick enough and 3/8 to 1/2 inch seems about right. This is the stuff that will isolate the noise from a possibly vibrating tank when the engine is running, so it’s important, you don’t want any metal-to-metal or metal to wood contact. I think the pictures Mike (XK-SS) and I posted before show fairly well how the different strips go on the tank. If I remember well what I read, the tank should be installed from the bottom and secured in place with the lower nuts

True. We use what we can. Although, the jute being 1/2 inch thick would compress and be as good as the 1/4 inch felt I am using. Here’s how it’s going in mine. The three pieces at the top get glued to the chassis and the lower two get glued to the tray. Thanks again to everyone.


Technical question about the felt or its absence. The person previously working on our car, 1952 FHC, did not put any felt in when the tank was installed. I do not envision any electrical problems, but is there something else that should be considered?

There should be a grounding strap on the front. The level sender needs it.
Abrasion and rattling from road vibration would be a concern.

Like this Rob? I followed your idea. The rear harness has an earth wire as well and this connects to the same point. Cannot find that photo right now.

Bob K.