Is there rubber in between those two discs? The ultimate question being asked is, Can the timing marks potentially be independent from the crank if the rubber fails?.
On a 3.8, yes. But maybe they fixed that problem.
Skene I think you need to pull the damper, and the tapered collar off the car and have a look. There seems to be something seriously wrong, and I would not drive the car until I found out what. They are not difficult to get off. The bolt on the crankshaft is a 1 5/16" socket. You donât have to pull the belt pulley off though if it has the locking collar you will have to undo 2 bolts that hold that on. I suspect that you are missing at least 1 key. The tapered collar has 2 keys, one for the crank and one for the damper.
I agree, worst case if it hasnât been off in decades is that it may be stuck with rust. I made a simple puller plate out of a square of aluminum with 4 holes for the 5/16" bolts. It rests against the large loosened nut, and as the bolts are turned in it yanks the damper right off so it hangs on the nut.
The best I could find is for the V12, but you can see how these are assembled:
Clearly two separate pieces bonded with rubber. If the rubber bond fails on one side, the two parts could certainly move independently of each other.
Not that its any consolation but the AJ6 engines also have the damper that can fail and result is the dreaded screech on start up.
Quote âThis damper should have been one pieceâ
If the damper was one piece then the ability to actually act as a damper would not be there.
So much good info here. Always appreciate it. The damper would have been off with the rebuild in the early 90s. It is likely original so an old geezer like me 
. I like the idea of pulling it and checking the tapered collar for a broken key. That would mean the inner and outer are slipping on the CS. I have never heard any squealing coming from the engine area though. Presumably the bolt is a left hand thread?
Rather than a broken key, Iâd have my money on a missing key, and consequently the damper has random orientation to the crank. If the whole damper is slipping on the crank, you wonât hear a squealing. That sound is more characteristic of rubber slipping and gripping on steel, and in the case in question it would be steel on steel. Looking at my photo in post #12 above, the bolt looks to be RH thread, but Iâm not absolutely sureâŚ
Incorrect⌠Normal (right hand) thread assuming you are talking about the large bolt that holds the harmonic balancer on.
Here is my âroughâ tooling for finding TDC on #6. The dowels were cut to the same length and I just marked them with a sharpie. It just had to check that they did not bind since there was some slop in the spark plug holes. I believe the dowels are 7/16 diameter. I put them in #4, and 5. And no I do not have the correct cam covers on mine.
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Hi,
On the XJ6 the timing marks are 60 degrees from the bottom. On the E-type they are (at least on cars from 1961 to 1967) in the middle pointing down, so on those E-types timing is set so the car is on a lift and you look from below and on an XJ6 you can set it by looking into the engine bay form the top, and the car on the floor.
Cheers!
I wonder if this is @azjag4pt2âs problem. Maybe someone at some point substituted an xj6 damper? The original post estimates they are 70 degrees out which is close. Someone might have manually rotated the dist by hand until it ran, and just disregarded the timing marks.
Sorry, I havenât measured at which angle they are on the XJ6, just that they point to the upper right when looking from the front when the E-types marks are straight down âat six oâclockâ.
Cheers!
Did you mean 60° from the top (like an S2 E-Type w/o AC)?
Hi,
Yes, if we use the somewhat familliar clock face metaphor the early E-types have the timing marks at âsix oâclockâ and IIRC the XJ6 has it at âtwo oâclockâ.
Each hour is 30 deg, 12 hours is 360 deg. although crank degrees are only half of the dizzy degrees so if the crank is 60 deg. off the dizzy is âonlyâ 30 deg. off, right?
Cheers!
I sent out my harmonic balancer years ago to be rebuilt. If you are using an original damper, it is hard to believe it is still doing its job? The idea is to âdampenâ if the rubber is rock hard that is not going to happen. At the time I considered a modern liquid-filled damper, but could not justify the cost.
Glenn
Hi,
In the case of the IL6 and even more so with the V12 I would not worry much about the harmonic balancer unless you very often keep it at 3.600, 4.800 or 6.000 rpm for long periods.
Jaguar did not have one on the IL6âs in 1932-1937 and only added it to the 3 1/2 Litre, the 2 1/2 Litre had none and they are good reliable engines. (1935-1951)
It has very little to do with the dual mass flywheels and balancing stuff on modern IL4, V6 and V8 engines, these old school IL6 engines run very smooth when everything is working like it should. Yes, it is designed to eliminate a harmonic vibration, which can happen, but on the V12 I donât think itâs needed really at all.
Cheers!
With #6 at TDC I ended up making a new mark on the pully using the sump pointer as a reference. Then I manually rotated the motor until the points closed on the compression stroke on #6. I used a test light similar to what the SM states. I stopped right when the light turned on to see where the mark was relative to the pointer. It seems you would want the reference position of when the points first close in the direction of rotation, but I could be wrong. If I use this static method mine is crazy advanced at ~20deg BTDC (probably a few degrees of error here). The manual states to rotate the dist with the test light connected but does not state the direction. Since the rotor spins CCW, rotating the distributor CW would advance the timing if I am think this correctly or again possibly bonkers. Since this did not make sense I fired it up, warmed up the engine, and hooked up a timing light to #6 to check the mark and my new mark danced all over the place near the pointer. At this point I gave up, washed my hands and grabbed a beverage. One thing I should state is that other than some idling roughness/splashing it runs pretty well.
Being too far advanced could explain your rough idle. Have you checked your distributer weights and Springs to makes sure they are well lubricated? You still have conventional ignition points? Confirmed you have a stable 35ish dwell angle and 0.025 point gap.
Spark occurs when the points open, not when they close. When the points close energy starts to build in the coil, when they open this energy is dumped into the spark plug because it has nowhere else to go.
Ideally it should be steady. A degree or two can be ok, but depending how much dancing you are getting, that may be some of your issues.
Tom