Agreed, 131 teeth.
BTW in the Mark II SPCs it changes in appearance.
Hi Rob…yes that scaloped shaped has courser teeth and on occasion moved…Jaguar reverted back to the finer 131 tooth unit…Steve
How are they held together? Induction welding?
Hi Rob,
Yes they are spot welded together. Last spring when I was reassembling my 3.8L MK 9 timing gear, our New England XK group discussed these plates and how to clean the V shaped sprocket oiling passageways, something often overlooked by people rebuilding engines. Paul Gavaza managed to break a serrated plate away from the backing plate by using a cold chisel. Of course they are not meant to be separated. I had to use a clock pivot drill mounted in a hand held pin vise to clean out my passageways, followed by several size wires. Another passageway often overlooked is the oil hole that runs down the length of the cam shafts.
Best regards,
Tom Brady
Interesting - Jag changed the design, then. My 140’s plates, two-hole, not four, came apart very easily by hand with no sign of any welds whatsoever. I bought new serrated sprockets from Crosthwaite & Gardner, beautifully-made parts.
The only indication of ANY bonding of the 2 parts are the small, circular indentations on the outer surface of the larger plate…nothing on the cam-side surface. My original 140 parts do not come apart and also have those circular markings.
Hi Lee,
Here are some pix of my serrated plates for my MK IX 3.8L. These are for two hole cams as originally used, as opposed to 4 hole cams used on later engines and as you have shown. You can see the oil passage ways in a criss cross pattern. Interestingly the 4 hole plate that you split apart does not have them. Jaguar must have deemed them unnecessary as lotsa oil is flying all around that area and they were prone to plugging up.
Roger King has plates that separate, which I have not seen before. Are there others out there who have seen these?
Best regards,
Tom Brady
Sounds like Roger is saying his original plates separate, but not the new ones he bought? Or maybe its the other way around, which actually makes more sense to me. Either way, Roger said his new plates actually used the original style of chain lubrication channels between the 2 plates…which surprised me at the time.
Also, the 4-hole plates are slightly larger in diameter as there was now no need to allow oil to flow around the circumference of the plate and then out to the chain thru the 5 holes in the sprocket. The 4-holers are also slightly thicker than the original 2-holers.
Another change is that the second set of holes were no longer “dowel holes” as they are a tad bigger than the other 2 holes.
Im not quite seeing this “chain lubrication” channel in the serated plate…yes i can see a tiny hole in the photos above…where is the feed supplying the oil? …i thought it was a just splash feed…Steve
Feed comes thru the cam, then out thru the V-shaped stampings in the outer plate. Later engines had a plug in forward end of cam. You can see this V in Tom’s first photo.
The teeth on my cam sprockets were quite worn, with evidence of hooking. I bought a pair of new sprockets from Crosthwaite and Gardner, here:
The holes in the sprocket can be seen in the photo on the webpage.
I pressed the original serrated cam wheels into these and adjusted their position until the timing was correct, using a timing wheel and dial gauge.
I misunderstood the ‘separation’ discussion - the serrated plates cannot be separated from the backing disc.
Gotcha…a real head-scratcher there for a while.
Indeed - they’d be really difficult to make in one piece!
