hot or cold !

[paulj]

Hi
have checked tappet's today Exhaust side rattling .
exhaust at .25mm cold book suggests .15mm normal and .25mm racing
any reccomends also is this hot or cold ( guessing cold )
it's a 4.2 series one 2+2 :?
regards Paulj

[christopher storey]

It is the cold clearance

[paulj]

Hi
thanks for the advice.
is there any body out there who really knows
the correct clearance for the tappets on a series one 4.2
after several phone calls today I am left with about four options
from 4 /3 thou to 13 thou all round
some for cams with 2 fixings different for cams with 4 fixings
help :?

[christopher storey]

Paul : generally speaking, if the camshaft itself ( not the sprocket) has two fixing holes only, it will be an earlier shaft. The later parabolic shafts all had four holes . However, there is one exception to this in that some early parabolic cams c 1971 only had two holes. The definitive way to tell is to identify the part number. If you examine your camshafts carefully, you will find that somewhere along the length the rough finish has been ground to a flat with a part number etched on it. Do not confuse this with the material forging/casting number which is embossed on the surface, often beginning with MC and a 5 figure number. Until you find it it is not easy to see and you may need a magnifying glass to read it ! For a car of your era the inlet camshaft should be C 14985 and the exhaust C 13081 . These camshafts require a clearance of .004 " for inlet, and .006" for exhaust for road use . If by any chance someone has fitted the later parabolic cams from an S2 or S3 XJ6 they will probably bear a part number in the late 30 thousands , or number C41680/C41681, and these require setting to .012" and .014" for inlet and exhaust respectively. Some people set the smaller clearances a thou or two up on the factory settings, but this does make the valve train noisier and is not necessary unless you are racing. I hope this helps

[paulj]

Thanks Christopher
I have checked the exhaust cam with torch and magnifying glass
the only numbers are
at the rear P31818A moving forwards what looks like a single D then last
MC20899 !!
have tried these numbers with sng but no luck the settings are currently
14thou for all the exhaust.
it taps from one or two of these when running and temperature doesn't change the volume. the car starts/runs/pulls well
so any ideas would be great thanks
Paul :)

[christopher storey]

Are they two hole or four hole type shafts?

[on2wheels]

Hi,
Paul if you go ahead with your tappet adjustment I would be very interested in the procedure.
Have you got the top timing chain tensioner tool and the camshaft setting tool?
My 4.2L rattles on the inlet side towards the cabin.
Someone has suggested adjusting the timing chain. Surely that would be a completely different sound?
So if you go ahead a description or photographs would be much appreciated. Then the outcome.
Regarding the inlet/outlet measurements does one not use the figures stamped on the data plate?
Cheers,
Nick.

[paulj]

Hi Christopher
the front sprockets are held on by 2x bolts which are wired
hope thats what you mean.

[paulj]

Hi Nick
the noise is quite pronouced and a screwdriver handle in the ear
the blade pressed against the edge of the rocker cover
found the area of noise, the gaps were set as per the book,
but there seems to be a lot of differing ideas on which gap for which year / engine/ camshaft, all got very confusing. also tappet guides qutie often get the blame.
timing gear was replaced when i rebuilt the engine, wasn't very difficult.
with my 4.2 the real problem is getting the cover because of two dowells at the lower section of the cover,
regards Paul

[christopher storey]

Paul : it is not the number of bolts which matters, but the number of holes for bolts in the front flange of the camshaft itself. You can fit 2 hole sprockets to 4 hole camshafts, but not fit 4 bolts to 2 hole camshafts. That is why you need to look at the rear face of the flange ( which is the only part you can see with the camshafts in place) to see how many holes there are. If there are only two, use .004/.006. If there are 4, use .012/.014. The answer to someone else's question about using the data plate clearances is that you have no idea what has been fitted to the engine in the 40 odd years since it was made, and so the data plate cannot be relied upon

[paulj]

hi Christopher
:D I have 4 holes! and sprockets with 2 holes
so 14 it is
thanks for all your detail
Paul

[on2wheels]

Hi Chris,
Would value your opinion on the following plan of action regarding my noisy tappets.
Considering I would not want to spend too much and go into engine rebuild territory. Also I am not confident of carying out the work myself.
A local mechanic, whom I respect, would carry out the adjustment if necessary. He has no Jaguar experience.

Here goes...........

1) Purchase all gaskets and cam cover bolt washers.
2) Remove cam covers.
3) Remove spark plugs.
4) Move engine until cam is on heal. Is there a better way of rotating the engine rather than engage gear and rocking forward or backward?
5) Observe type of cam. 4 bolt holes in flange = 012/014, 2 bolt holes in flange = 004/006.
6) If readings are too great re-seal and take to mechanic for adjustment.
7) If readings are ok consider noise to be other related items, re-seal and re-consider plan of action.
Thanks,
Nick.

[JEP41]

Hi Paul,

You should be able to turn the engine over to rotate the cams with a socket or spanner on the bolt which is located in the end of the crankshaft in the centre of the lower pulley.
Just a thought on the tapping noise, if you find all the clearances within the 004"-006" or 012"-014" range which ever is applicable to your camshafts. Just check the Cam Follower Guides, these are shrunk into the cylinder head. I had an engine in to investigate a similar tapping noise after the owner had overheated the engine. I found one of the follower guides was loose in the head and the cam lobe was actually tapping it back down every revolution. If this is the problem there are clamps available to clamp these follower guides down, SNG Barret sell them. :o

[on2wheels]

Thanks John.

[christopher storey]

Nick : I would be very reluctant to entrust this work to someone with no experience of XK engines, as there are a number of pitfalls for the unwary, the nastiest of which is forgetting that no part of the engine can be rotated once the sprocket bolts are disconnected unless BOTH cams have been released from the bearings .

It is an exercise which is well within the careful amateur's compass as long as you take your time and are methodical . First of all get yourself a camshaft setting tool which is a flat plate with a tang which engages in the slot you will see in the front flange of each camshaft ( JEC sell them) and so do Manners, SNGB etc . Adopt your steps 1 to 3, and then carefully measure and record systematically each valve clearance . Now get the cams to the position where the front Inlet and Exhaust lobes point outwards, at which time the slot I have referred to should be at 90 degrees to the cam cover face i.e. point upwards , and check this with the setting tool. Now remove the front dome, slacken off the chain locknut ( 1/2" whitworth from memory) and then press in the plunger and turn the adjuster to release the chain tension - I use a pair of needle nose pliers in the two holes in the adjuster . you can then undo the sprockets and release the cam bearings

Now comes the interesting bit. With the cams off, identify each valve where the clearance is incorrect and lift each cam follower bucket , one at a time ( I use a valve grinding suction cup) and measure the thickness of the hardened shim which lies in the valve spring recess under the cam follower . A digital caliper is useful here, but a micrometer is just as good if a little slower . Record the shim thickness next to the valve clearance - this is vital . If there is only incorrect clearance on say 3 valves, just deal with those valves . If there are many more which are out, record the lot because you may well be able to re-use some shims for other valves

You are now in a position to work out what shims you need. If the clearance is too big by say 4 thou, you need a shim 4 thou thicker than the one you have just measured . If 2 thou too close, you need one thinner by 2 thou etc etc

The major problem which can arise is if there has been valve seat wear or recession to such an extent that the valve is so high that you need a shim which is thinner than the normal range, which is 85 thou to 110 thou. There are people who have shims turned down, but this is a risky solution because you can end up with the bucket contacting the valve cap rather than the shim which can cause a dropped valve if you are unlucky. The other solution, short of new valve seats, is to grind the top of the valve stem, which is a bit of a bodge but does work and I confess to having done this on several occasions, but it really requires the head off and the valve removed to do this

Having obtained the ( theoretically) requisite shims - by the way half thou shims eg .0875 are much cheaper! it is then a question of reversing the process - REMEMBER NO MOVEMENT OF ANY PART OF THE ENGINE- and then when all is fastened together retensioning the chain - check the tension on the underside of the chain on BOTH sides, and you may need to fiddle about turning the crank both ways a little to achieve this, and then rechecking the clearances before replacing the covers

Good luck

[on2wheels]

Thanks Christopher for your very clear description.
Would a Timing Chain Adjuster tool help? ?15.58.

Nick.

[christopher storey]

Nick : I have never actually had the proper tool, but I certainly would not dissuade you . Once you slacken the locknut and remember to depress the plunger, it is not too difficult with needle noses

[attwood]

Hi Christopher (or anybody else who would like to comment),

I started to use my car in May last year after restoring the bodywork, steering and suspension. I had about 3000 relatively trouble free miles during the year but there was a bit of a tick from the exhaust side of the engine, so I have measured the valve clearances this weekend.

I have camshafts with two hole flanges but with the groove around the flanges, so the clearances should be 12 and 14 thou, as confirmed by a sticker on the cam cover.

The gaps I measured are almost all slightly too small, with the largest error being 6 thou on the exhaust side.

The shims which are fitted are all in the range 61.5 to 67 thou thick. I see that the smallest new shim available is 85 thou. I would be very surprised if the engine has been worked on - the indicated mileage is only about 65000 and I have no reason to doubt it. Therefore I assume that these 60 thou plus shims are original.

What do you think?

My favoured course of action at the moment is to have a few thou ground off the existing shims.

Thanks for any advice you can offer.

[1954Etype]

Dave,

I know of engine restorers who have ground the tops off valves in order to get within the standard shim range so can't imagine grinding shims down to get to the correct gap would be out of order. My only concern would be to look at why the gaps are closing up (assuming they were correct - 6 thou is a lot). This could be due to valve seats wearing. Your head must be fitted with the cast iron valve seats so doubt it is that. Worth investigating further imo.

[christopher storey]

Some thoughts :

1.I definitely do not think the shims are original . The smallest that Jaguar ever used, throughout the whole 40 year life of the XK engine, was .085 . However, I believe that a later "fix" was to use XJ40 shims which may be thinnner

2.If you are down to needing a shim effectively as thin as about .055 something unhappy is going on with the valve seats . Either that or someone has used valves which are markedly too long, which I think is unlikely

3.There are three ways you can approach this . The purist way is head off, thorough investigation, probably new seats ( which I am not enthusiastic about as there is a reported tendency for them to drop out if the engine gets very hot! ) and a rebuild using new proper size shims

A second choice is to buy a head from an XJ6 in good condition and use that

The other way is to leave well alone until the engine actually gives trouble by burning a valve. You may get many years of service yet before this happens . This obviously carries some risk of more serious trouble, but it is probably not very great

4.I should also say that the shims are very hard , and without specialist grinding equipment you are likely to do more harm than good by trying to grind them . They may also lose their hardness which could cause a lot of trouble .