XK120 single exhaust system

Finally, I have managed to fit a correct-style tailpipe for the single system (not the early side-exit design) onto my 120 OTS. As some of you may remember there was recently some discussion about what was the correct bracket for mounting the tailpipe onto the chassis. I think we managed to get to the bottom of that one. Very many thanks are due to Nick Saltarelli who sent me an original bracket all the way from Canada! This was my starting point. It mounts via the forward one of the two bolts holding the bumper iron to the underneath of the chassis.
The next step was to order a tailpipe from P D Gough of Nottingham, UK. They use an original Jaguar part as their pattern, which is also the case for the silencer. I was surprised to learn that the tailpipe is of 2" diameter. The outlet from my existing (and perfectly serviceable) silencer is only 1.65" OD, so I got them to make me a mitred piece to join my silencer to the tailpipe, stepping up to the larger diameter before the mitred weld. Crossed fingers and it actually fitted pretty well! They made the tailpipe too long at the back end, I guess so people can trim it to what they want. I bought one of those adjustable chain pipe cutters, where you squeeze the handles while rotating the tool about a quarter of a turn while the little hardened knife-edged steel wheels slowly do their work. I imagine it would cut through copper like butter, but the stainless steel must be so hard it was a bit of a struggle, but I managed it in the end. You don’t want the tailpipe to be the first thing to hit if you miscalculate while reversing, so I trimmed it to a little bit inboard of the bumper.
The pictures show what I believe to be the correct mounting setup for the single tailpipe. I have to say the Urs Schmid book shows an incorrect arrangement where the pipe actually hangs from the rubber bobbin, instead of the hanging bracket sitting on top of the bobbin. The XK120 Explored book barely touches on the single system at all, and the plan diagram of the chassis shows the tailpipe going almost straight back from the silencer and mounting to the floor of the spare wheel tray (which is how my old tailpipe was).


Stunning looking motor car

1 Like


When did they go from side exit to rear exit exhaust?

I am jealous of your final product. Plenty of time for me to get there.




Matt, from perusing the spare parts catalogue, it seems there were 3 different part numbers for the tail pipe on OTS cars: C3659 was apparently the side-exit type fitted to the alloy cars, then there was C4149 (also side-exit, I guess) fitted up to chassis 660983 and 672143, which is May 1952. Finally, the rear exit tailpipe C6672 was fitted to the end of production. There was also another tailpipe C5767 which looks like it was fitted to FHC and DHC XK120s.
BTW, my car is far from the final product - always something to do: re-wire, new top and tonneau, engine bay detailing, repaint (it is 2 different bronze colours at the moment) etc, etc…

It’s my understanding that on the original cars there were pinnacle nuts top and bottom of the bobbin holding the tail pipe in place. Just wondered if that’s right?

Not sure what you mean by pinnacle nut, Clifford?

Pinnacle nut is a type of self-locking nut made by Simmonds.

Not apparently on exhaust hangers, or at least not listed in the SPC, they just show ordinary nuts.

1 Like

When one takes something apart it’s standard practice to return the original fittings to the piece for reference. What I do, anyway. I still have my 120’s two original exhaust hanger bobbins - why I keep this junk, I don’t know, but maybe to answer questions like this one. They feature 3/8 UNF hex nuts and lock washers.


Thanks so much for clarifying this. Cliff

See below, PINNACLE NUTS are only used in two places on XKs, and not on exhausts…

They are used to secure the Fuel Pump mounting studs (2 off - BSF thread), and also as a lock-nut (1 off ANC thread) on the setscrew that secures the generators Adjusting Link to the generator housing.


Thanks much. I do have the one on the generator adjusting link. I will check on the fuel pump mounting studs next time I crawl under there.

Thanks Roger - good to know!

Small point Chris, the adjusting link setscrew and locknut for your car is most likely Whitworh and
take a 5/16 BSF spanner as do the petrol pump nuts, later models went UNC/ANC and take a 1/2"
AF. Not much difference in the thread rate of course.

Boy the stuff you learn on this site! Thanks, Peter.

1 Like