Morning all, how does one check?
Havent done this since the 90's on a landrover - was taught the rule of 9's which I cant remember anyway.... and the cylinder had to be TDC, but the XK is a different beast no?

P

 

• Rotate the crankshaft with wrench on the crankshaft pulley until the cam lobe for the valve being checked is pointing directly upward (90 degrees perpendicular to the camshaft cover surface), ensuring the valve is fully closed.
  
• Use a feeler gauge (blade-type) to measure the clearance between the heel of the camshaft lobe and the top of the tappet guide (or cam follower).
  

When you get to #5 intake, after first measurement; with a wood dowel and small hammer tap cam follower hard enough to cause it to open and snap closed with spring pressure. Do several times, then recheck clearance. If no change then I would suspect valve seat, valve ( if either were ground during engine refurbishment, or incorrect shim was added. ( could be valve seat that was ground but not fully lapped)

Best to see the results, before we all chime in with what we would do next!!!!
Rgds
David

 

I find this type makes things much easier when measuring.

 

The xk engine has shims and is only adjustable by changing the shim thickness. The adjustments are only required due to valve recession, the gap may close to the point of leaving the valve unseated, thus burning the valve seat.
The rule of 9 is for 4 cylinder engines I believe.
I may be wrong.

 

The clearances were changed later in the XK engine's life when Jaguar changed the profile of the cams. Originally 4 thou inlet and 6 exhaust, I remember they were larger on my XK 4.2 engine of 1980. 10 and 12 thou I think
Adjustment is a bit of a PITA because they are bucket tappets with a shim lying between valve top and bucket. So the camshaft has to be removed to change them. First of all you have to measure all the clearances when cold and write them down against each cylinder. Then, when you have the cams off, you take off the bucket that needs adjustment and measure the thickness of the shim. You then enter that against the relevant clearance measurement and can then work out what shim thickness is needed. Except, of course, it ain't as easy as that, because the shim is likely to be slightly worn where it contacts the valve. All Jaguar workshops used to have a box with all the shim sizes in it, and a table of sizes, each having a letter.
It can be a bit of a fiddly job, and two attempts may be needed, because the only way you know you've got it right is to replace the camshafts and measure again ! I've done it a few times, but it was many years ago.

There was an engine, who made it I can't remember, but it had the same bucket tappets system, but the shim was in a recess on the top of the bucket so was contacted directly by the cam. Replacement involved a special tool to compress the valve spring, to remove the old shim from the bucket, and fit another one in.

 

I've worked on many ohc engines and they can vary quite a bit as to how the shims are changed. As has been said, it's best to first check all the clearances and write them down on a crude diagram on a clip board. Then, on the Jaguar, the cams can be lifted one at a time to change all shims needed on that side. It doesn't take very long if you've organised things properly and I keep a note of what size shims are under each bucket, for future reference.

I find it difficult and tedious to turn the engine on the front pulley or on the ring gear so just dab the starter solenoid button a time or two while watching the lobes. Obviously this can only be done while the cams are still bolted down. I check mine regularly but have only had to change two shims, for just a couple of thou' thicker ones, in the twenty thousand odd miles I've done since overhauling the head. I did them with the loose head on the bench first, two thou' wider than needed, and then had to re-shim just two after they'd done five thousand miles.

Late addition - I should have mentioned that I always take the feed wire off the coil when doing this, just for the avoidance of a calamity.

Ray

 

To avoid endless tail chasing:
- Tighten the cams down between checks.
- Don't turn old shims upside down.
- Be absolutely systematic with keeping measurements and shims in order

 

From a competition perspective back in the day (Mk2s and XK150S), those factory clearances of 4 and 6 thou were never considered adequate, especially with big valve "gold top" heads and reground D-Type cams. Our practice was to aim for double that ie 8thou inlet and 12thou exhaust. Time was of the essence, extra clearance guaranteed no burnt valves or seats . . . and the logic has stayed with me since the 1960s.

Your most important tool is a micrometer (say 1") that reads to the thou. Use it to measure all the "worn by valve stem" thickness of all shims ie in the centre, not the rim. . . not only those coming from the engine, but all our stored supply of hundreds of new and used shims grouped in containers with thickness clearly marked.

• first, lift the exhaust camshaft . . . do not rotate either camshaft with both in situ!
• measure and record, for all 6 inlets, both the "worn by valve stem" shim thickness and clearance . . . . align each shim to its written position;
• compare measured valve clearance to desired . . . adjust using thinner/thicker shim from reserves . . . fit and replace buckets, but not inlet camshaft;
• next, refit exhaust camshaft, and repeat as for inlet side, finally fitting adjusted shims and buckets but not exhaust camshaft;
• this concludes what we regarded as the "trial adjustment" as a second stage was almost always needed.

To be "thou perfect" . . .

• repeat the process for inlet and exhaust in turn, further adjusting with new shims
• sometimes (but rarely with practice) a third rotation may be needed.
• finally, and using the camshaft setting tool, lay in and fix down both camshafts . . . marking the head with "VCs all set at xx/xx thou";
• if it's all good, now is the time to consign each "no longer required shim" to our containers of reserves, according to measure.

Subject to plenty of practice, we could lap in all the valves inside 30minutes, clean up, replace and collet all valves inside another 15, then set all our race clearances in 20minutes. Only rarely, the two of us did the lot in an hour. Of course, compared to road engines, we prepared our heads using two different stones to produce convex, thinner than normal valve seats, so valve lapping was fast but lasted only one meeting,

That was then . . . these days, no chance, if for no other reason that I have given away all our shims, and my fingers don't work as they did. No more "popping" the valve collets with hammer and socket, and no more two-man re-colleting using no tools other than manual labour.

That's how we maintained a spare head in reserve for the one that was out there racing. Fun days, but a great system!

Cheers and best wishes,

 

Very interesting, Ken, and all down to slickness and organisation. The more we do, the better we get.

I've got a big flat box that I made to house a huge selection of shims I was given by a pal several years ago. He'd bought them at a trade auction and they were included in a lot with a lathe that he wanted. I presume they came from a dealer who'd gone out of business and Alan didn't know what they were for. They cover just about all sizes from about .060" to .over 160" and there were many unopened boxes of 25 new shims of the same size, as well part boxes and an old biscuit tin of good, used ones. If anyone local to my area of East Anglia is stuck for shims, I'll be glad to help. I was pleased to discover they also fit my Hesketh bike, as well as old Ford engined Lotuses and other sundry Brit cars of the period..

Ray

 

Hahaha, just like you Ray, I'm happy to have shared all of mine to worthy new owners. IIRC those groups of new shims were stamped with letter codes that indicated thickness (as per manual) and were supplied in multiples in stout manilla brown envelopes. However, our stockpile lived in used tobacco tins, clearly marked on lid and encased in an old red toolbox. Many were new in their envelopes; used ones were loose . . . but if the lid said 125thou, then that's what each of the contents were.

I have been reluctant to disagree with the "never reverse the shim" dictum but reality must apply for those with only a limited access to many shims. By reversing a "valve stem worn" shim, you can often "pick up" 5 to 10 thou. If that gives a VC a tad too tight, a few minutes rub of the valve impressed side on emery paper will reduce the ridge around the valve stem impression and open out the VC by a few thou.

On another note, I never found anyone who, hand on heart, undertook the recommended "check and reset" pull down (was it at 1,000 miles?). I admit I only ever did it once and that was on my avatar Mk1 . . . a lot of effort that replaced only a few shims, but that engine then did 250,000 miles before retiring

Those engines, especially for track competition, emphasized a few issues too often overlooked on road engines . . . oil pumps, TC chains, sprockets, guides, tensioners . . . valves stems, guides, and especially, the profile, width and integrity of lapped valves and seats. IIRC, compared to about 5thou for normal road use, we banked on about 3thou oil film thickness when using the Caltex racing oils of the day.

Cheers and best wishes Ray,

 

Decades ago, a friend had a Lotus Elan, scrupulously maintained by one lady owner, but destroyed by various others. The few bits that worked fell in the 'time bomb' category. He couldn't afford anyone who knew what they were doing to work on it, so he passed it around friends (read idiots). Two of us, who had experience only of Minis and Imps did our worst on the cylinder head with the help of a Jaguar service manual (which actually covers about everything you need to know and is written out very clearly). Some of the shims in place had been turned upside down, probably more than once. There were also a couple of cup type shims. At first replacements seemed to be difficult to find, but one of us noticed they looked like those from his Imp. It turned out that they were interchangeable with Imp, Triumph Dolomite, Jaguar, and others that I can't remember. Some of these may still lead to useful sources (without the E type factor on price) though the makes are long gone.

One point that may have already been mentioned is that unless the head needs lifting for something else or the clearances are seriously off, particularly in the too tight direction, there's a lot to be said for leaving alone or going to what medics call cautious monitoring.

 

Something that hasn't been mentioned here, that Lord P needs to check...
When you're in there, make sure that no one has ground the top of the valve stem to gain clearance because a thin enough could not be found.
In some cases, the valve stem is ground below the spring collar, and any given shim will no longer make contact with the end of the stem.
When this happens the edge of the shim permanently rests on the collar.

If left this was, the keepers may come out resulting in a valve being dropped into the combustion chamber.

The repair for this is to install a fresh valve, and/or a new valve seat.
In some cases, the collar can be put on a lathe and material can be removed from the collar to gain clearance, however one must be very careful not to remove too much from the collar and weaken it.
No more then 15 to 20 thou.
I haven't looked at a collar in long time so I could not say for sure what is safe or not.

Also, take the plugs out so it's easier to rotate the engine, it may have been mentioned somewhere, but I'm too lazy to go through all of this.

 

As soon as my neighborhood helper comes by I will gauge the clearances, the valves came out of this head and i numbered them, I just didn’t know on the intake side i should number the shims and buckets (all new to me).

1 of the lobes is pointing up - I can’t get a feeler gauge in there at all, but I will make a note when I have a helper and report back.
P

 

A cardboard egg box for a dozen eggs works great for keeping all small parts separate.
Trust the o to1" micrometer for thickness of shim not the markings on the shim... a shim that is wrong for a given valve may fit another valve perfectly, just order new ones from Moss Motors, only the ones you need. ( if you buy a used box of 100 shims, the only one missing will be the ones you need)
As others have pointed out, if your at slightly over the target clearance target .004 -----.005 -.006 is ok, slightly below is no go. My experience is after you have finished and torque Cam Bearing cap nuts to 14.5 ft. lb. and checking clearance again, 50% will need redoing on second check. but you will be very close.
Rgds
David

 

"1 of the lobes is pointing up - I can’t get a feeler gauge in there at all, but I will make a note when I have a helper and report back."

This is a confirmation that you will have to remove camshafts to change the shims....After checking all 12 valves and recording the clearances and before you removing camshafts, set engine to TDC #6 with cam tool (notch in cam flange straight up) ...
After checking and installing new shims and rechecking, it is time to put it all togethers again.

Before you reinstall camshaft with engine still at TDC #6, place both camshaft in bearings with the notch in camshaft straight up using tool for precision.
Minor adjustments of Camshaft flange and Timing sprocket are ok to get 2 bolt holes to align.
Rgds
David

 

Over the years I've worked on many engines where the clearance has closed right up, especially on bikes, but if the bucket will still turn, even just a bit, the valve is ususally ok and a re-shim will fix it. It's always worth a try and, maybe, a compression check if you have the means. A compressiion tester is a good health checker and they're as cheap as chips these days from a tool store.

I was told by an old boy back in the '70s that I should only buy an old Jag if it had noisy valve gear, otherwise it had likely got valves that needed doing. There may still be an element of truth in that.

Ray