Lower timing chain slack

Hello Jag-lovers,

I’m in the proces of rebuilding my cilinderhead after a burnt valve due to bad valve clearance. I was planning to leave the engine block in the car since it was looking good to me. But I’ve found a lot of slack in the bottom timing chain.

Will this slack be gone when I start the engine so the hydraulic chain tensioner does his work? Or is this too much? See yt video below to see the slack.

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The hydraulic chain tensioner ratchets out under pressure and stays out even
when there is no pressure, so it appears that yours may be missing. I once
found one in the sump.

Mike Eck
New Jersey, USA
www.jaguarclock.com
'51 XK120 OTS, '62 3.8 MK2 MOD, '72 SIII E-Type 2+2

<https://www.youtube.com/embed/eYAyvnHdax0?autoplay=1&feature=oembed&wmode=o
paque> https://www.youtube.com/embed/eYAyvnHdax0

What he said…WAY too much slack.

As the chain stretches and the dampers wear, eventually the tensioner can simply pop out of its housing!
If nobody had every released the spring ratchet inside the tensioner tube,you could get this condition on a worn engine
either way, it’s not good I’m afraid you need the front cover off,or a good light or better still a remote camera in there,so you can see what’s going on in timing chain chest.

There we go again. From simply setting the valve clearances to a complete engine revision.

I will let know what the reason was for the slack in the chain.

Thanks so far.

With borescopes now selling for less than 20 bucks (use a USB port on your PC) they are a very useful tool for all kinds of things.

With the timing cover still on, cam cover removed, there is room to slip one down along the lower chain to inspect the tensioner. I did and confirmed that the ‘shoe’ on mine had gone AWOL:

It’s gone, but it’s somewhere…guess where?

Mine departed company many years ago when I gave the engine a bit of excersise, it came completely out of the body and fell down between the lower chain and the crank sprocket, snapped the chain and the engine stopped (obviously) Engine out and the first of two rebuilds. Been in the garage for the last 20 years and about to turn it 90 deg in the garage to start the process of replacing the metal mothed areas and the leather.

I’ve found the tensioner. It was indeed gone. See photo’s below. I think I’m am quite lucky that the tensioner didn’t felt down into crankshaft sprocket.

Any ideas why this is happening? The pad on the tensioner was not even worn out.

As Nigelplug stated, if the chain wears the amount of travel required for the tensioner to adjust can become too much, next thing the plunger has popped out. The timing cover can be removed with the head and sump in place I believe haven’t done it myself but plenary of information in the archives.

The Renold can and did fail due to the friction weld between the post and the shoe failing, in my experience this design either lasts a long time or fails during the run in period, the one which does not fail in any respect can be bought from Dennis Welch as fitted by Healey owners with no recorded failures, the pic is in the archive somewhere,

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Chain wear goes basically like this, that each link develops a little bit of wear or slop, say .001", and if you multiply that by the number of links, say 100, the chain is now 0.1" longer than it was when new.
The crank is always pulling on the cams on the exhaust side, so all of that slack will be on the intake side.
So the tensioner moves out to compensate.

Luck-EEEE! In two ways, no fouling of the loose pad with various moving parts and the plunger itself stayed in it’s body. Chain look OK?..do you plan further disassembly to replace some parts or is the head still on?

Thanks for the replies. I will go for a total revision since the head is already off.

There was no compression on Cil 3 so first I set the valve clearance for all cilinders but still no compression. I’ve found out that there was a crack in the exhaust valve of cil 3 so that was causing the lack of compression. Then I had found the slack in the lower chain. And right now the engine is pulled from the car and the head, sump and chain cover are all removed so im also honing the cilinders, replacing bearing, piston rings.

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You haven’t said if the plunger and spring are still within the shoe? If so, don’t think the ratchet mechanism can have been released by the last installer? Once it has been released properly,its highly unlikely it would stay inside the tube if the tube breaks free.

I’m sorry, I thought it was clear from the photo. The pad, plunjer and bottom end came out in total. The spring and bottom end was found in the sump. With bottom end I mean the part that is receiving the spring and has on one end an ellen key hole and is stepped on the side.

Ok it was just a thought. Couldn’t quite be sure from the photo. Sounds like excessive play in the chain. If the damper next to the tensioner was not set out, this can accentuate the problem as the chain wears.
Best Regards
Nigel Boycott

What do you mean with damper was not set out? Do you mean the damper on the picture?

Yes the damper that you’ve circled in the photo. When new, the tensioner has a spacer which these days is a piece of plastic. When the chain is fitted, the damper shown should be moved out to put some tension on the chain. (If you look at it, it has an elongated hole in it at one end for this.) once you have applied some tension but set the damper against the chain, you then slide out the plastic spacer under the tensioner shoe. The push to tensioner back until you will here a slight “click” this means than the spring is released by the retainer and will self adjust against the spring as necessary as wear increases, but will still operate hydraulically under oil pressure feed.
Best Regards
Nigel Boycott

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