Following a failure to release the clutch experience during the recent Monterey Car Week, I finally got around to putting an endoscope camera in the bellhousing to take a look. During the second half of the video I am operating the clutch lever outside the bellhousing:
The clutch fork has failed at the hole for the tapered pin. This fork was replaced back in 2005 with one of the light alloy versions available at the time. It has failed at the tapered pin hole just like 2 of the external operating levers have since 2005. I’ve scoured the archives for more recent posts on the topic, and from what I can see, in the absence of NOS parts, the “best” repro seems to be the Aluminum-Bronze casting that is stocked by Moss and SNGB (though both on back order) and Coventry Auto in the UK. I’m just checking here to see if anyone who has fitted one has an update on its status, or if any forged version is available.
David;
Bummer!! When I was rebuilding BOTH my engine and Gear-box, I looked long and hard at my XK120’s Clutch Linkage… I had a few bits and bobs, but they weren’t “better” than what I replace them with… sorta neither were “bad”, but neither were “good”, either!
I did contact a couple of folks who deal in used XK Parts and ordered the pins, etc. What I got “was” better, but not by a helluva lot (there is no “NEW” out there, any more!!)… BUT it was Better than what I had!! So I went with the “best of the worst”!!
My Engine/Gearbox was on a stand and I looked at them every time I was in the shop! Eventually, I fitted the Engine & Gearbox onto the chassis (along with other parts) and, as I passed the driver’s side, I’d depress the clutch pedal by hand… several times!! “full throw”… Nothing broke!! Still, when I go out into the shop and I’m “near” the clutch pedal, I “cycle” the clutch pedal several times… just-in-case… So far so good!! (this has been going on for nearly a year now… My confidence is growing ;-} Fact is, I’ll probably wear it out “testing it” BUT it won’t break until AFTER I refit the body!!! ;-{
Charles Ch# 677556
Having your clutch linkage go out on you during Monterey Car Week in front of potentially thousands would be one of my worst fears. Boy, do I feel for you. I can empathize as well since it was a developing issue on my other '120 I have in storage and I see it was an issue for my other car in the past as a previous owner went so far as to braze the exterior bell crank on to the clutch fork shaft. I should probably drop that pan underneath (it’s an early model) and have a look-see with the fork also.
On the car I have in storage it was mostly a matter of the fork taper pin having sheared on one end. I ended up turning a new pin, purchasing a new cross shaft, fitting longer oilite-type bearings at each end and taking Rob Reilly’s advice to purchase a used fork that came off a Mark VII as those are supposedly slightly beefier. Eventually I’ll be working on that car again but won’t know how well my repair was until other issues are worked out.
If I were to redesign the fork and cross shaft, I think I’d machine or cast a new fork out of thicker material around the cross shaft area and cut both the cross shaft and fork to take a square key as, 60+ years on, there simply seems to be too much shear stress concentrated around that lower part of the fork and especially the taper pin.
Forum search will show many of us have dealt with the same issue.
I had a couple spare Jag girls and upon careful inspection they were all cracked at the base of the arm … @ the hole for the tapered pin .
The light alloy versions are problematic. I bought on and promptly returned it. It’s a amazing the suppliers weren’t repeatedly sued for selling such an bad part.
The aluminum bronze fork I have used for near 10 years is from Coventry Auto in the UK. I believe they might be supplying the other Jag parts sellers. I bought from CA together with a new shaft.
I think the tapered pin sucks because it puts the stress where you least want it (at the most compromised area). i had a good shop drill a new hole horizontally theu, close to the center, and then we bolted it.
I also used the aluminium/bronze fork together with the XK150 shaft which has parallel-sided holes for non-tapered pins, which should be stronger. However, after putting it all together, I find when looking through the hole in the back of the bellhousing that the fork is something like 1/4" off centre… I can’t see a reason for this, unless the groove in the shaft which accommodates the locating bolt has somehow been machined wrongly? I don’t know how much of a problem a slightly off-centre carbon ring release bearing would be - obviously not ideal.
Thanks to everyone who responded. It seems that the only replacements are the aluminum bronze ones from Coventry Auto (also resold by other vendors) and the light alloy junk that failed in my car. No-one, including Coventry Auto, has the aluminium bronze ones in stock, so I’ll have to wait until they do. I’ll keep looking for NOS too, though I’m not hopeful. Thanks again.
I’ve no experience of that actual part, but have used Crosthwaite and Gardiner for several engineering components. They are well-respected, and well known for making parts for C- and D-type racing cars.
Thanks - that is the part. Yesterday, I found that same source, which comes with the C&G price tag! I may have to go down that road if nothing else works out. One issue with these components seems to be that if you don’t buy them all from the same source, they won’t be compatible. Today, I went through my notes from my previous clutch jobs on the XK140, together with my box of left-over parts. If found (and other accounts in the archives seem to back it up) that the taper pins from different vendors are different sizes (length, taper angle, and diameter all differ), and even have different threads. Some are 7/16-20 (UNF) and some 7/16-18 (BSF). I did find, amongst my old parts, a C9780 clutch fork which was on the car when I bought it. It appears to be one of the original forged steel ones, and in good shape. It is fitted with a non-tapered pin (as the XK150s were) which appears to be a modified 7/16-20 GKN bolt, with a 5/16" non-tapered pin section. So, this may be my way out if I can get a compatible XK150 shaft, pins, and actuating lever. If the XK150 pins are BSF threaded, I may be able to re-use the GKN bolt pin instead. I have a call into Coventry Auto on the parts I need. More when I know it…
…understood. When I searched the archives I came across your post on the subject in the pre-xk section. I wish our “usual vendors” knew this too. Some are supplying reproduction C.568 taper pins with UNF threads which, of course, do not fit the original BSF forks and actuating arms. Hence my comment about having to buy everything from one vendor or risk incompatibilities, even if it means buying parts you don’t really need.
Time for an update. Getting replacement parts was very frustrating. No one has a decent quality clutch fork, and everyone seems to source them from Coventry Auto in the UK. They didn’t have them in stock, and delay followed delay… I ended up ordering some parts from them, but may not use them for reasons I can’t go into here. I tried to remove the gearbox without removing the engine, but gave up when it became clear that my chances of success were not high:
I think I will reuse the parts I removed back in 2006 when the clutch first failed - just a worn out clutch disk that time. The clutch fork appears to be in good shape and the actuating lever (which has the D-Type part number) is welded to the shaft. The hole that the “barrel” fits in is a little oval, but will probably be serviceable with a replacement barrel in the adjuster link. Both parts are secured with the parallel pins with hex heads used on the XK150.
Back in 2006 I replaced all these parts with “new” parts from the usuals, because new is better, right? Oh, the innocence of youth… At least I was smart enough to keep the removed parts…
At least I was smart enough to keep the removed parts…