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Crankshaft Dampeners

Crankshaft Dampeners

Today I looked over the crankshaft-damper. Behind the damper I catch sight of a depression, and I think it was remainder of rubber (hard, deteriorated, may be because of oil). Can anyone tell me if there originally was a kind of damping rubber. I can't find it in the Parts Catalogue. P.2 (Plate A33) refer to 3 types of Damper Assembly, but do not has "damper-rubber" as a spesific part-number (May be it was implisit in the damper because of the balance?). An exch.part is expencive (G. Broad : £ 95+ 17%VAT). Is it risky do drive without or detoriated rubber (balance)? Are there alternative ways to restore the damper; or may be anyone does sell the rubber seperately? I can't remember this question is discussed before, so may be it's just a problem to me? In any case, thanks for any tips. - Martin Jacobsen, XK 120 DHC 1953 (she doesn't allow me to forget her in the wintertime)

Several companies will rebond new rubber to the damper. The damper is used to dampen vibrations and oscillations generated by the motor and relieve stresses built up on the crankshaft. The damper is used to smooth these out both to protect the motor and for the driver's enjoyment. If the car is run at high RPMs long enough with out a damper then the crankshaft might break. I had one go bad on my E-type and shattered the cone located between the damper and crank. Lot of noise and vibration after that until replaced. - Cleo Bay

Martin, Your description is a non-sequitor to me. The dampner, sold as a unit, is an inner ring (to crankshaft) and an outer ring (self explanatory) vulcanized together by a hard rubber. They can take alot of abuse. If yours is bad, you should hear noise at the front of the engine and feel lots of new vibrations. Why do you think yours is faulty? - George Badger

Hello George, Thank you for answering. Well, it isn't easy for an historian to know all things about engines - but I just looked at the surface of the rubber (for the first time) - and it seemed to be rotten. May be it is just in the surface. I didn't know it was vulcanized together. I've no noise or vibrations, so I think all is OK, But is was a good information, both about the construction and what will happen if the damper gets faulty. Thank you. - Martin Jacobsen

If you are speaking about XK engines ealier than the SIII XJ6, I do not believe the crank was balanced... - kind regards, Tony Parkinson, Vicarage Jaguar

"Particular care is exercised in the balance of the crankshaft assembly. The separate shaft is first dynamically balanced on an Avery machine. The flywheel, which has previously been balanced on a Micropoise Static Balancer, is now fitted and the assembly re-checked statically and modified if necessary. A final re-check is taken again after the clutch has been bolted in position." "The Metalastik damper, which is a proprietary unit, consists of a steel plate to which is bonded, through a thick rubber disk, a malleable iron floating weight. Variations of the weight, rubber volume, and mix, give these dampers a very wide field over which they can operate." From _The Jaguar Engine_, pg. 7, W.M. Heynes, M.I. Mech.E, C. 1955 Jaguar Cars N.A. Corp. - Mike Eck, '51 XK120 OTS, '62 3.8 MKII

Tony, Mike, et all. I have of course seen only two XK cranks, compared to others, but there were signs on my crankshaft webs of 'metal' having been removed, as not all the webs were the exact same shape. I don't know how much of this was due to the manufacturing process. There were also balance weights tack welded on the torque converter (at least I assumed that was what they were), Mmemory is failing (it was in 1994) and I didn't take pictures. The video I am thinking of has the pictures of the crank being balanced manually (ie being rolled like a bicycle wheel to see where it stops), and being rotated in a machine. I think they also got belted with a hammer and cold chisel. It is a Remarkable video. On saying that, I made no further effort re balancing other than to replace the torque converter and drive plate in the same position (5 years after removal), and of course the damper only goes one way. - Alastair Lauener

Some day I ago asked about a possible worn chrankshaft dampener. I took the car to a garage (not a Jaguar garage - the only Jaguar-dealer in Norway is 200 miles from me). Well, I asked them to inspect the dampener - and let them use my Manual. Having my XK at the garage is just like having a baby at the hospital, so the next day I did my first visit: The mecanic had used a puller, trying to get off the dampener. He hooked the puller-feet(?) on the outer (biggest) damper-disc. Yes, the outer disc did loose from the inner disc. Now I'm sure: the chrankshaft dampener is gone! ( so is the pulley) I'm of course protected from loss. We did estimate damages at £150 (parts). In one of my parts drawers I have a dampener from a S-type (3.8) with duplex pulley, in good order. * Is it possible to use a the dampener from the S-type on my 120? ** If I have to buy a new pulley - Do I have to get the pulley and the dampener balanced as a unit? *** What is the correct way to get the dampener loose (instead of a 3-armed puller). Is a /big/ knock with a copper hammer on the dampener a useful way with an eye to loosen it from the cone? Thank you for help, - Regards, Martin Jacobsen

I believe when the engines were manufactured, the crank was balanced with flywheel, clutch and the front damper on. I also believe that unless you are racing at max revs, the damper isn't so important. I would put on the S-Type damper, and forget. - Alastair Lauener

Martin, I have used a harmonic puller to pull the damper. Looks a bit like a crow's foot. Two 5/16" bolts are placed in two of the four damper pully holes. The large center bolt of the puller goes into the end of the crankshaft. Of course, the large nut on the end of the crankshaft should have already been removed. I have gotten lucky in that a light tap on the damper with a hammer has broken it free. Saved me from having to put on the puller! The damper off of a S-type will work. You will have to remove the S-type's pulley and replace it with the XK120's. I'm going to say that its probably not required to balance the damper with the new pulley but it definitely doesn't hurt. Both my XK120 and E-type went for several thousand miles before I got around to getting them balanced after damper changeouts. The three arm puller is a no-no when you suspect a debonding damper and if you want to keep it in one piece. If the metal parts were not bent when the damper separated, it can be rebonded with new rubber. - Cleo Bay, XK120, XK140

Martin, Well, they did a job on the dampener. Your pulley should be OK. The dampener should have been removed by threading the puller to the dampener and then removing the dampener. Yes, your spare dampener is OK to use but it should be rebalanced to your engine. This is a BIG job. Engine teardown and all that. I imagine you are not going to race the car or hold the engine at sustained high RPM's so you should be able to use it. I don't remember if the pulley will fit to the dampener. Common sense and the service manuaal is more prudent to use than big tools/pullers, hammers et al. - George Badger

A slight caution, Martin - Keep either the original crankshaft demper bolt or a similar-sized bolt in the crankshaft threaded hole to protect the threads; otherwise, Cleo's advice is sound. Beating on the (replacement) bolt head loostened a couple of turns (shock transmitted through bolt to crankshaft) with copper-headed hammer could help loosten the damper, and is, at any rate, very theraputic! :-) Best of luck! - Larry Schear, Twin Cam, Inc.

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