Two bolts, 7/16" wrench. Unscrew the tach cable first. You have the standard type with ordinary o-rings.
Only the earliest XK120 engines used a different cam cover gasket and W2483 was the last of that type.
Good to do these along with the new cam cover gaskets.
As always Rob you say it with pictures! Tomorrow I will mark the timing mark on block, bell housing gear tooth and smooth metal on flywheel, then remove the exhaust cam and begin removing shims. Thanks for the help. My husband thought I should just put fuel into the engine and make it run. Not as simple which he should know. Chasing Classic Cars and Motor Week are two of his fav shows.
cam lobe measurements not important nowā¦butā¦before they go back in. it will be good to know, ā¦a small caliper will do itā¦so laterā¦a caliper is better, you donāt want to scratch the lobe tip, but do look for any tiny part numbers on the cam shaftsā¦ok back to valve adjust and shimsā¦try to remove the shim so that you can tell which side was down against the valve stemā¦lifting out the tappet with a quite strong magnet is one wayā¦as the shim will often remain with the tappet. If the tappet lifts out with the shim still in place on the stemā¦fine. What you are looking for is a dimpleā¦: (could be on either side or both as I will explain) .and you want to know if on one sideā¦was it the side against the valve stem. The valve stem contacts the shim in the centerā¦so IF the shim is dimpled at the center from wear of valve stem to shimā¦it could be as much as one/thousandthā¦and you need to know if that is the case. So the center of the shim measurement is to see if the center is different from the outer surface thickness. Lets say from one valve position you remove the tappet and its shim and that shim is a .096 shimā¦it may have .096 etched, or a letter which corresponds to .096ā¦if the shim is flat on both sides then fineā¦and you check it with the micrometer and it is in fact .096 thick in both center and outerā¦okey dokey it is a .096 that was there and you have now removedā¦and will calculate to what is needed as a replacement. BUT if the shim is dimpled and if you were careful removing it so you know that the dimpled side was against the valve stemā¦and you micrometer the center and it is .095ā¦you have to use that .095 as what that shim really was in operationā¦(even tho its outer thickness or etched size or letter designation is .096)ā¦the valve stem was on the .095 center. This will be what you use to determine what shim will be the replacement. IFā¦the shim had the dimple side against the stemā¦and the other side of the shim has NO dimpleā¦is flat and true, then you could reverse the shim side to re-use it, as either a .095 or a .096 when reversedā¦you flip itā¦now the dimple is against the inside of the tappet (follower) and the dimple is thus irrelevant so it is effectively a .096 shim. So back to what shim you replace it with to achieve desired .006 intakeā¦if it was dimpled by 1/1000 , with the dimple having been against the stem, then you treat that existing shim as a .095ā¦and use .095 as what the old clearance was based on, .and put .095 on your chartā¦(with a note it was actually a dimpled .096 shim). As I have mentionedā¦it is possible in prior valve adjustment, that the person doing it had already reversed a dimpled shimā¦the dimple could have been on the tappet side, not the stemā¦and in that case the dimple did not affect the clearance. ORā¦due to prior use, and prior flipā¦a dimple could be on BOTH sidesā¦in which case the shim center measurement is NOT what it is because one sideā¦will be in toward the tappet and will not matter. In this case, of both sides dimpledā¦I would not use that shimā¦it would be hard to know its center valueā¦there are waysā¦(put say a flat feeler gauge across one sideā¦measureā¦then subtract the thickness of the feeler used) ā¦maybe it used to be a .096 when newā¦and now it is, in the center .094ā¦1/1000 dimpled on each sideā¦but if installed acts as a .095 (one dimpled side is against the tappet inside and is thus irrelevant. whew ! Nick
So once you get BOTH cams out, I would then turn the crank about 60 degrees to place all pistons well down their bores. Now you can do your valve adjustment one cam at a time without any fear of valve-to-piston contact. This will allow you to install the cam with new shims, turning the cam as many times as you like, measuring gaps after each turn, until you get consistent readings on you gaps. Once satisfied with the clearances, remove that cam and install the other one, repeating the routine as above. In short, you should do all your cam and shim work with those pistons well out of the way. Just remember to turn the crank back to TDC before final installation of both cams.
The other advantage of having both cams removed is you can now apply compressed air into each bore to identify any valve or ring leakageā¦transmission in gear and rear brakes locked, of course.
hi Leeā¦that is a new one to meā¦I have never seen this method suggestedā¦not by Paul Saltwick, nor Pat Harmon in their textsā¦nor anyoneā¦so, .I have been on the "NEVER turn engine at all in this process once cams are off sprocketā¦I understandā¦that when cams are outā¦all valves are closed thus no valve in the way of a pistonā¦but in turning the engineā¦how and when do you know that ALL pistons are sufficiently clear of valves when a cam is turned.? It seems to also raise the issue of turning the engine back (reverse of what you did) exactly the sameā¦TDC mark must be exact as it was. Andā¦if what you suggest is doneā¦what does the timing chain do on the sprockets ? Do you mean the cams are not on the sprockets? How do you turn the cams against the valve spring pressure? Andā¦if doneā¦Iād think you want to first turn backā¦opposite to normal rotationā¦so that when you turn to return to TDC it is in the normal operation directionā¦so that chains/sprockets have moved as they should. So interested to hear moreā¦Nick
Geez Nick write a book! It Oakes a lot of words to explain accurately. I am just kidding with my comment.
The cams are out thanks to Robās picture. I looked for a number on the cams. Intake has one, the number 3 as does the Exhaust cam however the latter also has SE where the intake cam does not. Interesting.
I am measuring the shims and lobes on the exhaust cam now.
Maddy
Once the cam sprockets are secured by use of, either a 3/8" fine-thread nut, or are wired in some fashion using the grooves in the center pins(if equipped), (to the convenient āearsā), it is simply a matter of going slowly and carefully as you rotate the crank. The big circlips hold the serrated plate to the sprocket. I have rotated the crank many times with timing gear installed without the camsā¦you just have to be slow and cautious. And you donāt necessarily HAVE to reverse the rotation to get back to TDCā¦one could simply continue normal rotation until TDC comes up againā¦BUTā¦it WOULD take nearly 2 full rotations(possibly tedious) to place the dizzy rotor back to the original position.
There is always 120 degrees between successive TDCs so thatās why anything approaching 60 degrees gives loads of room for the valves to openā¦though 60 degrees is certainly way more than actually needed if one was worried about reverse rotation issues getting back to TDC.
Forgot to mentionā¦the early engines have such weak valve spring that the cam is easily turned using 3/8" bolts or studs threaded into the bolt holesā¦either using hand strength or a lever(screwdriver). One could also use a rubber-cushioned vise grips to turn the cam.
Those cam markings are common but are not the c part number which is tiny and near the front on the rough.
They are the only numbers on the cam. Unless I soak the cam in my parts bin and wire brush the rough area like I did to see the 3 and the SE is the only positive way to look for a number. No guarantees Iāll see one either.
In case the shim numbers I teerst others I am posting my findings.
You forgot a ā0ā after the decimal on intake 2 and 3 flat. But to Nickās point, IF you have shims dimpled on ONLY one surface, simply use the āflatā measurement and position the dimple up towards the bucketā¦two dimpled surfaces = a scrap shim.
Lee it is a digital micrometer with an led display. I recorded the number in that display. I did zero out the micrometer before measuring.
Those 2 shims measure almost an inch as recordedā¦looks like you can reuse all the shims IF they meet the proper thickness requiredā¦just face the dimple āupā and go with the āflatā measurement.
I thought maybe so. I will tell in time.
Hello to Maddy Please see my email to you this amā¦I re-stated your clearances and existing shimsā¦to insert numbers into the chart. Butā¦we need to study ā¦Intake #1 where the clearance was zero and the shim is about the thinnest normally available. Also remeasure the shim on Exhaust #1ā¦too much difference in the two measurements to concludeā¦Nick
Following Nickās directions there was s a discrepancy with the #1 intake clearance. The initial gap is .001 which is .005 difference from the spec. .006 which would require a .082 shim where the smallest is what, .085?
What should I look at to indicate such a discrepancy?
Thanks
Maddy
Intake spec should be .004" so you are .002" closer than you thought. A .084" or .083" shim is called for here. The thinnest normally available is .085", but you may be able to find a .084" or .083". A smaller than spec gap is often caused by seat wearā¦not fixable without head removal.
At that small a difference I would find a machine shop that has a surface grinder and ask them to scim the required amount off. Place the ground side on the opposite side of the valve stem.
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Nick;
I have adjusted the valves on ONE XK with the head still on the engine (my 120DHC
back in 1968!!)ā¦ Royal PITA!!
All other Valve Adjusts, Iāve done, have been with the Head OFF the Engine (I have a
set of tools used during valve/head work that fit into the bolt holes on the underside of a
head [cast iron or alloy] and hold the head up off the workbench about ten inches, or so,)
Charles Ch# 677556.
Maddy;
When you measure a shim and find the āsmallestā shim available is too thick, the āarea of discrepancyā is the Valve Seat (aka āValve Seat Regressionā)ā¦ The āGypsyā in me says a Valve Job (new seats, possible valves, etc) is in your immediate future. ;-{ Some folks will grind-off the āstem endā of the valve to gain clearanceā¦ NOT RECOMMENDED!!
ALSOā¦ DO NOT USE the āhalf thouā adjusting shims that are āout thereāā¦ these are off non-Jags and the outside diameter of the shim does not āwork & play wellā in the Jagās top spring keeper!!
Charles Ch# 677556.
as to the #1 intake at near zero clearance: 6 āthatsā": Charles is correct that some of the non Jaguar shims have smaller diameterā¦that can cause the shim to rock off the valve stemā¦and that
makes the shim become tilted, and that will quickly cause destruction of the keeperā¦and that will drop the valve and that will destroy a lot of stuff. Rumors are that Dick Maury has thinner shimsā¦will check. More rumors: older Saab, or Alfa, or TR-7 shims may workā¦with the caveat of the smaller OD to be looked for. We will have a good look at the stem but will not grind it. We decided on 006/008 for clearances. (True that Jaguar revised to 004/006.) Letās just sayā¦that we have to live with something like .002 on the #1 intakeā¦the rest all at 006/008. The rest of the initial clearances are quite close to specs and will be adjusted. Yet to be measured is the tappet deck thicknessā¦itād be so nice if had the thicker one at present. What may be the effect of a lesser clearance in that one, #1 intake? Noticeable? if so in what way? (a compression test has not been done yet). The goal is an engine that runs nicely for a Sunday drive.
Nick