Hot cylinders 1 & 4

Others can reply with more detail, but afaic, its not abnormal for one side of the chain to have more slack, depends on the exact rotation point of the motor

I did find this out myself so many years ago I forgot which one, but this can cause a slight misalignment in the cams when all is tightened up

The way around that was to do a couple of things, which I think involved having the tension on the chain the clockwise direction, doing the ex cam 1st, then the inlet cam, (but I could have got that order back to front :grinning:)

Torque fitting on those cam bolts should be about 35 foot-pounds.

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Torque - do you know the strength rating on the sprocket bolts?
Torque charts have recommendations based on strength ratings and also amount of lubrication or lack thereof.

Never torqued a cam bolt in my life.

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After adjusting top chain tensioner ( NEVER tension in a clockwise direction!) turn engine over at least four times.
Set bottom end on TDC no6, using the timing pointer as your reference.
Check cam positions with gauge.
By turning engine over 4 times, this will even out chain tension. But MAY slightly alter cam position. Hence need to use gauge to check.

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What is the reason for this?

just seeing the post re clock-counter clock: so—…clockwise and counterclockwise (as well as right hand and left hand ) are defined in the Jaguar Service manuals (pages noted here-in) and owners manuals and service bulletins…as determined by the driver seated in the driver seat and looking forward. The engine crank damper, fan, flywheel --turn counter-clock in operation, again viewed from driver in seat looking forward–Period. Well–not so fast–most of the time working we are NOt in the drivers seat. So…if viewed from say the front of the car–looking back…rethink what it is…I don’t even want to say what it looks like from there–because it is the incorrect viewpoint. But ok…here goes…if at the front because that is where we are when tensioning the timing chain or working on camshaft to sprocket set bolts–then engine rotation is (ugh–hate to say this–clockwise-- ugh. In general the engine should only be turned in the proper operation direction.
BUT…The manual say s t is ok to turn the engine SLIGHTLY back and forth when tensioning the timing chain…(B-31). This also must be done as one loosens or tightens the 2 cam to sprocket bolts (2 each side).(B-41and B-50) and at other times as may be needed (finding TDC or lining up timing marks, noting that a Final chain and cam alignment tool checks should be done with a final engine rotation in the proper operation direction. One can always think of proper rotation this way–the visible teeth in the flywheel via the inspection hole come appear coming from the top moving downward–no matter your view-front-back-or side. Cam bearing caps (must be in same location and orientation as they were–marked to match cyl head marks) are torqued at 175 inch lbs max.(B-47). The manual refers to the timing chain adjuster–stating to tension rotate the serrated plate anti-clock: hmmnnn from what viewpoint…as at that moment one is in front, looking back to engine and the adjuster ?? have to check that out. The distributor rotor operates counter-clock as you look down at it.
Nick

Thank you for your post. Yes, I agree that it is recommended to never turn the engine backwards but I have not seen an explanation as to why the tensioner eccentric needs to be turned in only one specific direction and am curious as to why.

I would think it is so that there is no slack in the section of chain between the 2 cams, the exhaust cam is pulled by the inlet cam, which in turn is pulled by the tensioner sprocket & thus the crankshaft sprocket, keeping the whole lhs of the chain system in tension.

Sorry, but I am unable to visualize how turning the eccentric in one direction vs the other would make any difference to that explanation. Are you able to provide a diagram showing how that would work?

I am confused about what is discussed–turning the ENGINE or turning the eccentric chain adjuster–or both–: Service Manual B-25 -Remove Cylinder Head text, and other sections have text about releasing chain tension, and tightening tension…with references to clock and anti clock (which given the manual statement that references are as from driver in seat looking forward–is a question for me–when looking at the eccentric chain tensioner–which view is it?) Small engine rotations “backwards” meaning clockwise can be done to set timing, cams, etc, but finally adjust of any setting must be done in normal operation direction–counter clock as from driver looking forward (flywheel teeth coming into view from top-moving downward.) There is some archive discussion on adjusting timing chain tension methods–to tight but not dead tight and how to achieve that–while at the same time maintaining exact cam notch alignment. Probably should move discussion to a new topic? or resurrect archive on adjusting timing chain, about which the manual text–is supplemented by discussions here in the archives.
Nick

The discussion was a result if a post warning to never tension in a clockwise direction. I assume that to mean turning the eccentric as turning the engine is used to verify tension not adjust it. Perhaps I misunderstood the post.

Perhaps @Nigelplug, who lobbed the “NEVER…” Comment into the ring and then disappeared, should return to clarify what he meant by his comment. Then, those more knowledgeable than I can comment on whether they agree or not…

don’t know what was meant–but–to adjust timing chain tension…there may be some back and forth of the engine–back in only small amounts–with the FINAL tension, and any final cam adjustment (always check cam alignment after a chain adjust) to notch with tool–always done in proper engine rotatation…counterclock as from driver in seat. As to the timing chain adjuster–the eccentric serrated plate with the release pin and two holes for the special tool–that can be adjusted either way to loosen tension or tighten as may be needed. The advice to rotate engine in proper direction 4 times is good advice. The top chain adjuster eccentric is often stuck and when so required careful coaxing and PB blaster etc, ALWAYS when working in this area be certain the abyss into the timng cover-sump is blocked and sealed off so that no bits can drop down–towell and saran wrap.
Nick

Replaced all the valve clearance shims as required, checked the gaps and reassembled everything. Absolutely no difference ! Even though the compression check was good I am now wondering if the exhaust valves on 1 & 4 are not sealing for some reason, allowing combustion past and into the exhaust header.

A leakdown test will determine that: you’ll hear the air escaping through the exhaust system, if that’s the case.

Yes, I think that’s the next step thanks.

I’m not sure if this is relevant, but I just discovered when sitting in the car that the heater blows cool air at tickover until you increase the rpm to about 1500 when it blows really hot. I guess that possibly indicates poor water circulation, could that affect just those two cylinders somehow ?