And you can confirm it’s the firing stroke by checking the rotor arm is pointing to No.1 plug lead.
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So much easier to use, 1”19/64’s what’s that all about 
Well Robin you know what my dear old Dad used to say …
“Give them 25.4mm and they’ll take 1609.34 meters”
And by the way my wife and I are planning a trip to NZ in the spring so get your guest room ready 
Casso, with all due respect I submit this is true only if the crankshaft and the distributor are in sync, which of course we expect them to be on a well-running engine. But once we start disturbing things all bets are off. I believe the best way to determine whether #1 is at TDC, as Grooveman suggested, is to use a gauge like a dial indicator or a poor-mans variation of such.
Ah Grasshopper … the top and bottom of my engine are in eternal harmony …
Cams are aligned using “Wonder Boy” my homemade cam tool.
The Ittsy Bittsy stamped triangle on the front of the engine (that I never even knew existed) also aligns perfectly with the metal reference pointer.
I must now go and meditate on this.
I NOW feel very comfortable about undoing the cams from the timing chain and removing the head.
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Grooveman, you have belt, suspenders AND your waistband has been stapled to your midsection so if you weren’t ready to go forth by now I’d say there’s no hope! 
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Which spring yours or ours? And where are you landing?
I agree a DTI gauge is the best way of determining TDC, what I was pointing out was that No1 cylinder can be at TDC on the exhaust stroke as well, so just to be certain its the firing stroke you can check the rotor arm position.
An excellent point sir. And if it was the exhaust stroke the camshafts would be in different positions than they are for the firing stroke and the notches wouldn’t line up, correct?
Mike
Quick question …
I’m getting ready to disconnect the timing chain from the cam sprocket and take off the head this afternoon (finally) and I’m curious about the upper chain tensioner.
Do I just undo the two bolts and pull it out ? The manual talks about using an allen key and winding in the plunger ? A bit confusing.
I think thats to facilitate replacement. From memory there’s an ‘O’ ring in there that it will pay to replace. Just be careful when you undo the bolt as there will be tension on the plate.
The tensioner has to be ‘parked’ by using an Allen key to turn it clockwise until it locks. This compresses the spring and holds all the components together. If not done the tensioner will fly apart as you remove the plate. You may lose some parts into the engine.
Head is finally off 
It looks like the gasket failed between the water galley and the number 1 piston …
You can see how a little coolant leaking into a cylinder steam cleans it …
And what a little WD40, Scotch Brite, and elbow grease can do
A bit more work cleaning up the top of the block and it should be ready to go. No scoring on any of the cylinder walls and the original machine crosshatching is still there. Also surprising there is no detectable rim on the top of any of the cylinders.
My friend who helped me lift the head is quite knowledgeable about car engines and was literally shocked at how good everything looked. When I told him it had 160K miles he didn’t believe me.
The head and valves look very good, nothing burnt and no corrosion, just carbon buildup I dropped it off at the machine shop this morning so I’ll really know what needs to be done in a day or two. That thing is surprisingly heavy !
The only thing that showed any wear was the upper timing chain tensioner …
It looks really worn, but I don’t see any easy way to replace it.
Thats a different place or the gasket to go. Not surprised that the cross hatching is still visible, my 2.9 still had it at 300,000 klms
Groove, my engine’s upper chain tensioner looked the same as yours. I don’t think there would be any harm is letting it be. I replaced mine, but it requires the removal of the timing cover which would significantly add complexity to your job.
I’ll never forget that when I ordered the new chain tensioner from my Jag parts specialist, the guy said it was the first one he recalls ever selling!
Thanks Brett …
I was surprised that there wasn’t a simple way to replace the tensioner’s face without removing the entire thing.
After thinking about it it does appear that the two tracks where the roller part of the chain travels over the tensioner aren’t worn down that much. So I’m not going to worry about it. Was the wear on your’s kind of rough like mine ?
Mine looked pretty much identical to yours.
Absolutely correct Mike, but I’m guessing our forum may be used by some users/ owners who might not understand engines and valve timing as well as you do, and was merely pointing out an easy way to determine the firing stroke when checking TDC.
Grooveman, my apologies for being so late to the party, I’ve been so self-absorbed in my own “No Spark” issue I didn’t even know you had this thread running.
I want to chime in with a couple of things. First off when I replaced my head gasket I gave absolutely no thought to where the position of the #1 piston was or the position of the cams. The car sat in the garage for two years after blowing the head gasket until I could get enough time and courage to tackle the job. Here are pictures of how bad it was here. http://www.jag-lovers.org/snaps/snap_view.php3?id=1360620362
Like you, I took my head to a shop here in town that specialized in milling and valve work and they did a great job. It was now time to put it back together and only then did I have to think about all the timing issues. I did find the same drawing of the timing gauge but didn’t want to take the time to make it. Now here’s the thing, the engine, without the head on or the distributor in place, doesn’t have a firing stroke and an exhaust stroke, it just has TDC for #1 piston. Whether it’s the firing or exhaust stroke is determined by the cam position and distributor. The first thing I did was position the piston at TDC using a dial indicator (see photo)
When I was satisfied I had TDC (within .001") I rotated the intake and exhaust cams on the head until the notched were straight up (all valves closed) the compression stroke, and bolted the head on. Then made sure the distributor rotor was pointing at #1 when I installed it. When it was completely together it fired up on the first try.
Grooveman, a word of caution here. Be clear I’m not saying this could happen to you but let me share my experience with you. My chain tensioner looked like yours when I replaced my head and I decided not to replace it. A couple of years later I was on a trip out of town enjoying the drive running at 75 mph on cruise control when I started to climb a long hill. I was at a higher altitude then normal, about 7500 feet and the grade became more steep so the Jag shifted to a lower gear. Somehow in that process of downshifting I believe there was enough slack in the chain and the strain of the uphill grade to cause the chain to shear the pad off the chain tensioner right down to the metal allowing enough slack in the chain to strip the teeth on the cam gears taking the engine out of time and stalling. Being unable to get it started again the tow home was $400.00 and that was the easy part.
http://www.jag-lovers.org/snaps/snap_view.php3?id=1435093667
I had to pull the timing chain cover to fix the problem and they said it couldn’t be done without pulling the head. Long story short I did but it was not easy. I’m not sure if you still have the head off. but if you do, I would replace the chain tensioner.
On the other hand, if you are an easy driver and don’t hit the passing gear very often, then you may never have an issue.
