Timing chain adjustment

[mouton]

Don't be non-plussed. The tensioner operates on that length of chain which naturally lies between the sprockets . When it is turned it moves eccentrically downwards to increase the distance that the chain travels between the sprockets . Unless in so doing it moves a camshaft ( which ideally it should not do , it is only the tension in that part of the chain between the sprockets which is affected . I think it is a problem of nomenclature really : the adjuster does not really tension the chain - it would be more accurate to say that it takes the slack out of it. If your chains on the outer side below the sprockets are whip tight, which they certainly sound to be , then in some way the chain is over-tight. There should be a small degree of flexibility demonstrable by pushing inwards with a finger . At a rough guess I would say you should be able to see the chain move between1 and 2 mm and spring back again

Alan, You can use a metric socket to move the clamp nut on the adjuster -- 17mm or perhaps 18mm, I forget. But you don't need Whitworth tools for that. [Answer to an old post, but...] The tension on one side or the other of the cams does not make any difference, despite the service manual statement. Where the tension is located depends on the location of the cams, and which way the lobes torque the cams in that position. Slack is "fungible", because if you turn the engine some little way the slack will transfer sides, or even move in to the center area where the adjuster sits. The service manual technique does not specify where the engine should be set and so cam position could be anywhere. What matters is that the chains not be dead tight. And that involves getting all the slack on either side of the cams out, but allowing a small amount of slack overall. My technique for that is to make the chains dead tight -- turning the engine and retensioning until all slack is gone, and you can't move the chains on either side -- then backing off 2-3 clicks, which gives you the slack you need. At that point after turning the engine once you should be able to move the chains on one side or the other with a long screwdriver. What you have done is reliably met the factory specification of "not dead tight". Worked for me for the last 40 years...

Jerry

[mouton]

Can anyone tell me how difficult it generally is to get the cam-covers oil-tight ? I'm used to all sorts of leak-issues in a variety of engines made over the last 50 years, and some, and some locations, are more prone than others, hence the question. With new gaskets, seals, flatted cam-cover surfaces, and scrupulously cleaned head sealing-area, do I need anything dramatic on the gaskets ? Hylomar on both sides, or some Loctite sealant everywhere ? Please put me in the ball-park so I get it right first time !

Another approach to oil leaks at the valve covers is to use Cometic gaskets. Cometics are thin aluminum covered with teflon, all very thin. No sealant is necessary because the teflon coat takes up any variation. They are very sturdy too and can be reused perhaps indefinitely. I got them and no leaks for years. Available from Terry's Jaguar in the US, XKs Unlimited (Sets only) and perhaps SNG Barratt? As with all the gaskets attention to the ends at the rear is most important. The half-moon seal and o-ring should always be replaced, and the gasket carefully set into the groove for the half-moon seal and carefully trimmed to the opening for the left side plug, to seal properly with the o-ring. (This is for the 3.8, other versions have different seals) Put the left valve cover on first and tight, then carefully slide in the plug with new o-ring. With Cometics you have to trim the rear ends yourself and care really pays off. Done once and finished. Watch out for using RTV/Silicone sealer. Its characteristic is to pooch out when the fasteners are tightened in the form of tiny silicone balls or worms that can detach and become floating plugs in your oil system. They can also jam in the relief valve and cause low oil pressure. I used to use RTV all the time until I saw the results myself in the relief valve.

Jerry

[ALAN COCHRANE]

Jerry

Thanks for the info.
I've tried the alternative method suggested by Chris and found it very difficult to reduce the slack to an acceptable level. As you correctly point out the slack transfers from one side or the other depending on which way you rotate the engine.
I'm assuming you slacken off the tensioner and then rotate the engine, re-tighten the tensioner and repeat until all the slack has been taken up.
At that point you move the tensioner slightly clockwise to re-introduce the desired amount of slack.
I've had a look at the service manual and as you've pointed out it only says "not dead tight"-not very scientific.
Did you check the cams afterwards for TDC alignment?

Alan

[mouton]

Alan,

It's not the direction you turn the engine but exactly where the cams stop. I loosen the nut until it's just free and tighten the adjuster until all the slack that can be removed is out, letting the pin hold position (why release the tension?). Then I crank the engine a little and repeat taking out whatever slack has appeared. I do this a few times and find that all slack is out, none can be felt on either side. Then I back off 2 clicks and tighten the nut again. I've been doing it this way for maybe 30 years. No noise, no wear on front cam bearing. I initially set the valve timing with chains tightened this way, of course. I have checked the cams and I find that you have to have a lot of slack in there to have a significant effect on relative valve timing. If you adjust the top chain every 10-12K miles you should not see any variation in valve timing that makes any difference.

Jerry

[ALAN COCHRANE]

Jerry

Your method sounds like the way to go. I found that when you disconnected the cam toothed drive assembly, it was very difficult to transfer the slack to the chain between the sprockets. If you can remove this stage then it should be much easier to take up the slack and then, as you say, re-introduce "not dead tight" slack. This may also remove the rotational noise that I'm now hearing. I thought this was due to me fitting the crankcase breather filter mesh the wrong way round during re-assembly-wishful thinking unfortunately! I'm running short of time to get the car ready before the Scottish Jaguar Day on the 29th. If it's not ready we'll have to go in the Boxster-God forbid!

Alan

[mouton]

Alan,

FWIW, getting a rotational type noise in there has been for me an indication of the chain too tight. Too loose resulted in a chain-y slapping sound. But that's just my experience. I have a Boxster, too. For me it was a shining light of style after decades of dreary looking cars, so when they got cheap I had to have one. So glad I did, as they are the most remarkable car! Still sad to have to use one on the Jaguar tour!

Jerry

[ALAN COCHRANE]

Jerry

Interesting what you say about the noise. It's very intermittant and sounds like two metal surfaces lightly rubbing together. Perhaps I've overtightened it after all. I know it takes very little adjustment to go from slack to very tight, having spent a whole weekend fiddling with it. I need to check the tension again and go from there. The chain was quite slack on the inlet side before I started-it felt as if there was about half an inch of sideways movement with finger pressure alone. Although it's hard to judge since you can't actually see it. This sounded like a bit to much play after reading all the posts and the Workshop Manual. The original noise was only audible after the engine was fully warmed up-which would make sense. Unlike the current noise this was constant and sounded like a typical chain rattle-not surprising really since that was what was causing it!
I totally agree with you on the Boxster-phenomenal car with build quality to match. IMHO it's head and shoulders above it's rivals. I was never a fan of Porsche until it came along and this is our second one. It's also very reliable and can easily be used as an everyday car.

Anyway I digress. I'll let you know how I get on.

Alan

[ALAN COCHRANE]

Jerry

Top marks my good man. I re-adjusted the timing chains using your method and hey presto both the rotational noise and original rattle have both disappeared.
I've now got a noisy alternator. This is a bit surprising since it was bought new from Hutson's less than a year ago. It's a Lucas 11AC with the separate 4TR regulator.
I fitted a three inch pulley so I could retain the original 3.8 single V belt and tensioner idler wheel. Could it be over-speeding and has now started to be noisy? I still have the standard 3.8 crank pulley as far as I can tell, maybe someone can tell me what diameter this would be?

Alan

P.S. I found the source of the noise using my new mechanics stethoscope-a brilliant piece of kit for ?5.

[Tim T]

this is an old thread,but can have some info added to it :- the above post assumes that the verier adjusting assy will actaully move freely.. often they wont after a few decades of use and crud build up. I'm currently recommsioning a 3.8 that was last registered in 79 and has approx 85 k miles on the odometer( old service records confirm this as correct mileage) .. after going through all the usual systems I ran the engine and found the top timing chain to be noisy ..giving that familar tinkling noise at certain rpms.. upon removing the breather cover i discovered the locking plunger was seized in the depressed position (IE..it was NOT locking the vernier wheel in place).. when I went to turn the wheel with the standard jaguar tool, I discovered it was jammed in solid.. so someone had been in here in the past and gave up on the job after discovering vernier wheel was seized in place.and managed to jam the locking plunger in at same time..The remedy was to remove the wheel (after carefully placing a shop towel in there to catch any parts that may slip out of the fingers) and then the locking plunger and its spring which was stuck in solid.. it took pair of small vice grips and a lot of tapping and wiggling before it finally started to move and I was eventually able to get it out of the chain support body ..and it was pretty mashed up by the time it broke free and I was finally able to get it out.I replaced the vernier wheel with a sacrificial one from my parts stash..after liberally dosing the shaft with penetrant.. I then hit it a few times with a sharp chisel and 2 lb hammer in clockwise rotation ( this would slacken the chain) ..it would not budge.. so I backed off the nut further so it was level with end of threads and whacked it with a copper hammer to try and shock the assy and break it free..the slack in the nut was taken up and the hammer and chisel was tried a second time .. this worked and the wheel moved very slightly after a number of good hits .. I then did same on opposite direction and kept moving it back and forth, adding penetrant, until it was loose enough to turn with the tool.. I was also careful to collect the shards of metal that broke of the vernier teeth from the chisel action with stick magnet.. then I removed the sacrificial wheel, fitted replacement locking plunger and spring ( after rotating it sans spring in its hole, to make sure it would move as it should an lock the vernier wheel ) and then both replacement plunger and spring assy were replaced along with the vernier wheel..chain adjusted, and r/h valve cover removed to check chain tension. seemed about right..all was assembled and the engine ran again..much improved but still some chain noise after running the engine about an hour overall.. today I repeated the same thing again..had to remove the vernier wheel and repeat the performance with the sacrificial one again..( though locking plunger still free and doing its job) .. upon start up the chain noise is now completely gone.. I have not yet removed valve cover to check tension, but will do so tomorrow.. an overly tight chain will put excess loads on the idler and other components.. so i need to check that is not the case.. and rectify as required..

[PeterCrespin]

i discovered the locking plunger was seized in the depressed position (IE..it was NOT locking the vernier wheel in place)..

No disrespect Tim, but where technical issues are concerned terminology can be important. What you describe is not the Vernier assembly but the toothed tension adjuster plate. The E-type has verniers on the ends of the cams and torsion bars only, not the serrated upper chain adjuster plate (controlling an eccentric adjuster).

The eccentric works in both directions, depending how the engine was last assembled. If it is untouched since the factory then it follows the manual. If it was last turned fully the opposite way it will still tension the chain but following the manual would slacken rather than tighten the chain.

No biggie, but the less ambiguity the better, I think.

[Puddinhead]

"The eccentric works in both directions"

Hi Peter,

1966 FHC: What am I doing wrong ? Block at TDC #6 compression stroke (#2 + #3 pistons both at their lowest stroke) and #6 cam lobes are pointing outwards.

New chains, lower chain no problems.

However, upper chain has problems.

I can adjust the eccentric shaft and transfer the slackness on both sides.

However, when one cam has one bolt holding the sprocket gear in place, the opposite side sprocket gear cannot properly bolt as the chain has now become too tight to allow the sprocket gear to exactly mate to the camshaft vacant cam hole !

It seems the chain is maybe the wrong length ? As even when I have increased max amount of slackness; I still end up with one cam sprocket bolted(1 bolt) and the remaining opposite lacking enough slackness sprocket lacks to mate sprocket gear to the vacant camshaft.

The chains are new, do you think I got a bad (length) upper chain ? I still have the factory chains, 54k miles. Head was off for coolant damage welding (and new sleeves/pistons/crank regrind).

Many thanks,
Patrick
'66 FHC

[mgcjag]

Hi Patrick....have a look in the Jaguar service manual, if you dont have one look in the knowledge base section, technical, manuals......page B27...".the holes must exactly line up, if they dont then turn adjuster plate through 180deg which due to the construction of the plate will facilitate alignment......worth looking at re different sprokets http://www.georgiajag.com/Documents/Camshafts.html Steve

[mgcjag]

To follow up on Patricks problem...the post above mine....its now running on the US forum https://forums.jag-lovers.com/t/problem ... fhc/356119

[valerea]

Hi

Just seen this in my search for information on what torque to set for the central nut between the cam sprockets

Can anyone help please as I can’t find any reference in the manuals?

Thanks

Paul

[mgcjag]

Hi Paul i see youve also posted on Jag lovers and had answers...there is no torque figure in the service manual for the timing chain adjuster central nut.....I just tighted be feel.....Steve

[valerea]

Hi

Yes I did. I was worried about lack of specificity. Spent loads on this and don’t want to get it wrong!

I usually find the jag lovers forum really helpful

Paul