Timing chain problem

Any ideas?
I am having, a lot of trouble getting the top timing sprockets onto the cams. When I removed the head I didn’t adjust the tensioner and when I came adjust it I found it, was seized. It is now free and I think at full slackness. I can turn it left till it tightens or right till it tightens, so slack in the middle, is that right ? I can only get one sprocket on and not the other. I have fitted new chains and counted the links and they matched the old ones.

That sounds correct. Might just have to keep trying to ease the sprockets on, not sure why you would be having trouble, even with a new chain the centre distances should still allow it to go back together.

I had similar trouble with my Mk2 last year after upper and lower chain swap (masterlink chains), along with bottom tensioner. They did go on in the finish. Paul

Could it be because of that composite gasket?

I thought it might be so I tried it with no gasket and still wouldn’t go on ( and wrecked the gasket) .

The eccentric cam 18 is free to rotate all around?
I don’t think it is possible to mix up the idler sprockets 17 & 25?
Cam sprockets on backwards?

The adjuster cam will will go 360° if I take the chain off it. I don’t think the sprockets will go on backwards.

make sure the sprockets fit on the cams without the chain.
if they fit and there is no head gasket I would try another chain

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Some progress I think. I am still undecided which type of gasket to go for.

Looks good, was it just a matter of trial and error?

NO. Still doesn’t work.

Have you tried with the original chain?

The other thing is the chain dampers, is there any adjustment in those?

They are not touching the chain.
I think a composite gasket is 1.8mm so the difference between no gasket in my previous trial and the with a new gasket is 7.2mm . It’s quite a distance. I am going now going back to David Manners to check the length of a new chain against my old one. Foolishly I only did a link count and didn’t check the length.

Hi Jim, this is really weird. As I said on the phone I’ve no experience of Jag timing chains (yet), but something’s wrong here. It’s a pain, I know, but if you have the old chains still I’d strip it as little as possible just to swap over to the old chains without changing anything else. That cam should not be cocked up like that at the back and I think you are at risk of damaging something, not to mention wasting expensive gaskets. Take the gasket off - I don’t believe that’s relevant, as there should be plenty of movement with or without it.
If it’s still wrong with the old chain on, I’d take everything off and try again with no tensioners fitted at all. That should leave a lot of slack. Is the centre wheel at the top of the lower chain adjustable? Is it possible to have too much tension on that, which would stop the upper chain fitting?

The new chains have a removable link, so I could split the chain and feed another through. The old chain doesn’t and I don’t want to cut that incase the new split link is different. To change the chain the whole front has to come off and I think the sump. I will keep you posted.

In DM now and the old and new are the same, so buying more gaskets for the bottom end and strip it again.

Jim. I had exactly the same problem on my XK120. I had the head overhauled, including skimming, I bought a composite head gasket from Rob Beere and couldn’t get the chains on the cam sprockets. I called Les Trafford from Trafford XK Competition Engines. He came and eventually got the chains on but they were way to tight. He brought a tin gasket with him and fitted it and was all good. He said he had never had this problem with a composite head gasket before.

I think it will be tin gasket for me. I am getting rather fed up with it now .

That’s really weird, I have recently put a head on my 3.4 and used a composite HG with no problems at all, its as if the head has grown in thickness.