Finally got back around to the Jag this afternoon. Took a while to gather the gumption (apologies to Pirsig ). You will recall I had 0 psi on #1 and #4 cylinders, and 120 each on 2 and 3. Pulled the cam cover today in preparation for pulling the cams to do a leakdown test. Here's what I saw:



So yeah, the secondary chain broke and headed for parts unknown. I guess that helps explain the 0 compression...
My questions start here....
First, am I correct in assuming (hoping?) the exhaust cam "settled" in a spot where valves on 1 & 4 are held open enough to prevent compression, but not enough to interfere with pistons?
Second, from this point can I remove the exhaust cam safely by simply removing all the journal bolts, or is it held in place still by some part of the timing gear? I still want to do a leakdown test...
I still intend to remove the head regardless of leakdown results -- I just want to try to know ahead of time that it's OK in there re: valve stem condition.
Current plan of attack includes the obvious timing kit, and I also will buy the head gasket set which also includes all the other miscellaneous seals, O-rings, intake and exhaust gaskets, etc. The set I'm looking at is Eurospare, with OEM-style head gaskets. I saw something on here last night suggesting to use MLS gaskets instead -- is it really worth the extra cost, or will the OEM gaskets provide good reliability? I don't mind doing the work -- I'd rather not have to do it twice.....

 

You can remove the exhaust camshaft, but more than likely one or more valves are bent. You won't know for certain until the cylinder head is removed. Be sure to find out where the rest of the Bank 1 secondary chain is before moving the crankshaft.

What is the condition of the other secondary timing chain and tensioner?

From my personal experience, I prefer to use OEM JLR parts, especially gaskets and seals.

 

So far I have removed only the passenger-side cam cover. I'll pull the other side tomorrow and have a look in there as well. I have a local shop lined up to do the valve work if it needs it -- they've done a lot of Jags and are very familiar with what needs to be done. I would rather put the money into other stuff the car needs, but if I find bent valves then it's off to the machine shop...

 

Today I pulled the exhaust cam off the passenger-side head (the one with the broken chain). All the tappets rose to the same level as I removed the cam -- roughly 5mm off the deck. I haven't pulled them off the valves yet, but I wonder..... If one or more of the valves is bent and therefore stuck in some open position, wouldn't its tappet sit at a lower level than its surrounding mates? All 8 exhaust tappets sit at the exact same level, and cannot be pushed down under (firm) thumb pressure.
As I've said all along, I plan to pull both heads if for no other reason than to clean the chambers and piston crowns, and check bores to make sure they're good for another 100k miles.
I guess I'm not good with mysteries, and this kitty is slow to give me definitive answers.
On a slightly different and positive note, I pulled the drivers-side cam cover and the chains are both intact. And, by the way, the broken secondary chain on the passenger side is in one piece and only broke in one spot. A single link... See pic to follow...

 

Broken secondary chain:

 

So far, at least, this whole project is kinda fun. That being said, ask me again how fun it is when it's snowing, my wife is still using my van every day to get to work, and I'm still commuting by motorcycle because I have a non-functional Jag in the driveway.....
NAH....... I'm still very hopeful that this Jag will leap once again. It may take a few weeks to fettle the motor issues, but once that's done it's just a simple matter of replacing pads, rotors, calipers, and brake hoses all around and strapping on a fresh set of tires (tyres?) and we'll be on the road.
Once I get the timing gear and heads off and actually know for certain what the valves look like, I'll start a build thread with pics. This is my first V8, but I'm no stranger to DOHC 2-litre 4s, so this is just 2 of those right?

 

I have noticed that about half the 4.0 engines with broken timing chains have the exhaust cam stop in a 'HAPPY' place.
I bought a 1999 XJ8 with a broken 'B'bank secondary chain for $500 and just replaced all the chains/guides/tensioners. No valves bent and I still drive it 10 years later.

good luck

bob

 

Awhile back, one of the old members (Danielsand) had this issue: he was able to fix and reinstall the chain and lucked out: no bent valves. My independent guy (Abacus Racing) told me, at the time, his experience was the same as Bob's -- about half the time people are lucky!