I have read with interest many posts about changing Jag timing chains, tensioners, etc. (trying to decide if I will ever attempt this as a DIY project). With a search engine I have just now read responses to a thread by Chester86 entitled,"98 XJ8-What is a camshaft adjuster magnet?", dated 11-25-2010.

The response by motorcarman (bob gauff) suprised me by this statement: "The crank is at 45 degrees after # 1 TDC with the locking tool installed in the torque converter drive plate at the correct oblong slot and the cams are timed accordingly."

I suddenly realized I had never before read anything in the posts about TDC crankshaft timing marks in posts about replacing timing chains and tensioners. Does my 02 XJ8 4.0 have timing marks? If so, are they on the flywheel or on the cranshaft front? Also, "at the correct oblong slot" suggests that there might be an INCORRECT oblong slot lurking somewhere (feble attempt at humor). A little guidance on this point, please.

In my younger years I rebuilt several engines successfully, but all had keyed slots for the sporckets and TDC markings at the crankshaft front. Now I notice that no one has mentioned a timing light, either. I am really getting old! Thanks

 

Yeah, I'm getting old too but gave up on timing lights many years ago. The engine's timing is determined by sensors related to the crank shaft and cam shafts positions. No more timing marks on the harmonic balance pulley.

The crank shaft is locked in place with a bolt-like device through the flex plate (fly wheel to us old guys) and the cams are locked in place with 'timing flats'.

The tensioner change is not difficult at all. The hardest part is screwing up the courage to get started. Plenty of help around if you need it.

 

Alvin

The cam/crank timing is a relationship. It does not matter if YOU see it at a certain time, it only matters that it is syncronized!!!

Some people will only set the calander/clock at the Winter or Summer Solstice.
Others will say NO!!! you have to use the EQUINOX!!!!

The V6 Jag engine uses dots on sprockets and copper colored links on the chains to align the cams/crank.

I have installed timing belts on engines with white lines on the belts and notches on the sprockets!!!! THAT"S IT!!!!
It does NOT MATTER where YOU want the cam/crank to be at a certain time. It only matters where the designers/engineers want to reference the timing marks.

You can take your engine apart and scratch/stamp any timing marks you want (Bottom Dead Center??)

As long as you know how to align the cam/crank, the engine will operate normally.

bob gauff

 

I think there's only one oblong slot, but FWIW, if the camshaft flats are close to being aligned, the "correct" oblong slot on the flywheel will be close to alignment with the crankshaft position sensor hole which accepts the locking device mentioned by test point. While bob is right, the designed reference points minimize the amount of thought and precision/accuracy required.

 

Testpoint, Motorman (bob), and ttl, I thank you one and all for your prompt, informative responses. I appreciate it more than I can say! Now all is clear to me.

Times do change: I am now in my 79th year, an auto repair nut since about 1942. During the war years, as you know, no new cars were sold. I worked one summer at the local Chevrolet dealership's paint and body shop. Few new body parts were available (NO chrome). I watched those mechanics scavenger parts from everywhere to keep some of them running. They were ingenious with swap-out engines, transimssions, etc. to keep a car on the road. Body repairs went out with unbelievable thicknesses of body lead (before the advent of Bondo). To this day it bothers me to live in such a throw-away society. Today mechanics remove and replace but generally don't repair as they once did.

I remember when I bought a 1994 Lexus I asked at the dealership how to hook up my oscilloscope. The shop foreman said, 'We don't even have one here! All specialty diagnositic equipment. I knew then that both my 'scope and macho timing light were museum pieces (they are getting a little dusty out in my garage).

Old people get garrulous, don't "they"?