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Clutch Springs

Clutch Springs

Dear XK Experts: whilst sorting through some odds and ends from my disemboweled XK140, I checked over the clutch cover assembly (no numbers stamped on it) and was expecting to see 12 YELLOW springs (# BB 447890) behind the pressure plate but found 12 BLACK ones instead. May I ask: since I bought this otherwise O.K. clutch assy. at a local Jagswap, have I been duped yet again, the 140 parts book says "Yellow springs" and in my past dealings with clutches, I've always found either that the whole spring has been painted or just a spot colour on a coil or two and without releasing the springs to examine them more closely, I'm going to assume that the coils are in fact all black. So, have I got the wrong springs for a 140 (no O/D) or have I got springs that just happen to be black instead of yellow? Is there a difference in the strength of clutch springs between models using the Borg&Beck 10/98C cover assy? What is the dimension for checking the bearing surface of the release lever plate to the datum of flywheel friction surface? And finally, what do those with more experience of XK clutches think is the more appropriate friction plate surface for longevity and non-combat driving, grooved or plain? Those who read the recent thread on XK crank balancing might be interested in the photo and description of the clutch/flywheel balancing method on pg E.22 of the MK VII/XK 120 workshop manual, I presume that the mandrel must be an accurate fit to both the flywheel and driven plate bores with the clutch cover assembly and driven plate being concentric for the best results. Thank you in advance for replies and allow me to get in early with my Xmas Greetings and Best Wishes to all at <xk@jag-lovers.org> - Regards, John Morgan

P.S. What's the correct spelling of "mandrel"? The text in the workshop manual mentions "mounting on a mandril..." I always thought that a "mandril" was a fierce ape with a colorful face so don't try this at home folks.

Clutch springs: XK140 - PB44: plate is BB 47627/46 - 6 springs (illustrated at Plate M). Yellow springs in pressure plate. There was just one type for the XK140. XK150 - 3.4 standard cars had yellow and light green springs (VI120), 3.8s had black springs. Seems like the black springs might be heavier than the standard yellow, but that's a guess only from the above. - Regards, John Elmgreen

don't worry about it..it is probably an aftermarket pressure plate. You could go to a specialist and have them check the springs or just buy a new one if you are unsure. These are pretty standard stuff and relatively cheap. The mandrel is just used to center the clutch in relationship to the pilot bearing and the pressure plate so the trans can slide in. (Try to remember an old girl friend) Go to your local parts house and get a universal clutch alignment tool. This will have several different sized bushes that screw onto a shaft that in turn aligns the clutch so you can bolt the pressure plate to the flywheel. The bush goes into the pilot bearing mounted in the end of the crankshaft. It's not a big deal..been done for a long time. good luck. john shuck..beijing

Hi, John - If I remember right, the original 3.8 liter engined XKEs had 1600 pounds pressure (total) from the six black springs. I modified my car to use a Corvete pressure plate with a total of 2400 pounds total pressure, plus greater swept area. Only rework was to smooth the flywheel (larger swept area) and mod to throwout yoke to accept a true thrust bearing throw-out assembly, insterad of the carbon block. 25 years later and no problems ('course the car hasn't run in 23 years!). Your assumption about the black springs being stiffer than the light green or yellow ones is correct, but the count is 12, not 6. My XK-140 Spare Parts Catalog identifies them as p/n BB.44780 (Yellow). Cheers! - Larry Schear, Twin Cam, Inc.

I don't know if anyone has replied on the latter question of the originating posting but the correct spelling of the word mandrel is just that -- mandrel. - Dick Clements, '51 Mk V 3.5L Saloon

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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