Valve train noise??

[peters3103]

How can this be determined?

[Durango2k]

Very carefull and Accurate measuring of both parts- bucket and Guide.

Tolerances are shown in the Workshop manual.

Carsten

[peters3103]

So the term "bucket" is the tappet guide and "guide" is the valve guide?
I've never personally rebuilt a cylinder head before although I removed the one on my MK2 20 years ago and had it rebuilt so still have my "L" plates on!
What is required to make these checks? All advise greatly appreciated.

Pete

[PeterCrespin]

1) I hope you have re-adjusted your chain correctly now. This was not logical advice when searching for a tapping noise IMO.

2) The valve guide is out of sight under the valve spring. The tappet guide is the tubular ferrous item visible and pressed into the alloy head to provide a rubbing surface for the inverted tappets as they move up and down under each cam lobe.

With the cam covers off you can check valve clearances and whilst the tappets are unloaded you can try poking alternate sides with two screwdrivers to make them rock in the guide. Some perceptible movement is permissible and I doubt you will find there is markedly more movement in specific locations although you might. Careful measurement is your only true diagnostic technique as Carsten said.

Has anyone else heard the engine and confirmed it sounds unhealthy? Is your inexperiences leading you to chase a noise that may be on the spectrum of normal sounds?

[peters3103]

Thanks Pete, I have a clearer understanding now. I found a youtube video showing the process of measuring tappet clearances and changing shims so can now see how it goes together. I will do some more checking. Yes I have re-adjusted the chain and yes I have had a Jaguar mechanic listen to it and he advised to tighten the chain just to eliminate this being the cause. I have been over it with my stethoscope and am convinced it is tappet noise from exhaust valves 2, 3 and 4 although clearances are ok. As I mentioned previously, at idle the noise cycles in and out and when the revs are increased it becomes constant. I will remove the cam covers again and do some more checks. The noise is definitely outside of acceptable parameters. Although I am inexperienced in this particular area I do know an XK engine that is too tappety - I have owned about 25 Jaguars since my first S1 XJ6 in 1982.

Cheers
Pete

[tinworm]

You may find that the exhaust cam follower/guide wear is much more pronounced than the inlet side. So check every one carefully- the wear will mainly be at right angles to the camshaft - as the camshaft rotates it wipes the top of the cam follower and this tries to push the follower sideways so the most wear is on the ''thrust'' side. If remedial treatment is required the guides can be overbored to take a wider diameter cam follower, I had some done at Chessmans with 1.4" cam followers installed- this is much cheaper than new guide fitment.

regards Barrie

[PeterCrespin]

the wear will mainly be at right angles to the camshaft - as the camshaft rotates it wipes the top of the cam follower and this tries to push the follower sideways so the most wear is on the ''thrust'' side.

The tappets rotate, so wear on those is even around the periphery. It shows up as 'barrel-shaped' tappet wear, as shown by the pattern of rubbing around the side and by careful micrometer measurement near the top, middle and lower rim of the tappets. The guides do wear more on the thrust side but are harder to measure than the tappets with DIY equipment. Internal micrometers used for cylinder bores are usually too big and calipers are a bit iffy for irregular wear patterns. But if you can get a specialist XK engine reconditioner to install new oversize tappets in staked-down ground-out guides, then that's definitely a good idea.

Pete

[christopher storey]

Your description of being able to press the chain runs inwards by about 5/16 sounds very very slack to me. There should be just perceptible movement under light finger pressure . I should readjust the upper chain tension before you do anything else, and see what this achieves. Next, your reference to very slight marking on inner surface of the top of the tappet guide needs investigation. There should be NO marks at all on the guide. I should have a look with a magnifying glass at both the marks on the guides and at the surface of the lobes of the corresponding cams. If there is any evidence of corresponding marking then it is highly suggestive of the guide having become loose. What then happens is that the guide then floats up and is hammered back by the cam lobe abutting on it. A hold down arrangement is then the only safe cure

[David Oslo]

I am following this live thread with great anticipation and expectation!!

Pete's description at the start of the thread is spot on to what I have on my S1 4.2 The rattle comes & goes at certain revs, low idle can be quiet, and then just 100rpm higher it will rattle, then it can go away, to reappear. No change to cold or hot engine however.

I have stethoscoped extensively, problem being that solid metal is good at transporting sound, and the audible noise actually deafens most what comes out of the stethoscope earpieces. It's not like a knackered bearing, dead easy to spot. But I do tend to get more distinct noise along the valve covers, and towards the timing chains.

I'm parking the car for the winter in a few weeks and pulling the engine to put in a XJ6 S1 MOD box. At same time I will pop of the heads & sump and give it a top and bottom overhaul. So maybe I will spot something obvious in the inspection, knackered tensioner, dodgy tappets, worn cam or similar. Will post if I find something, otherwise this thread may get there first.

[peters3103]

Thanks all again.

Christopher, as I mentioned I tightened the upper chain to dead tight just to eliminate this as the cause. When I ran the engine I could hear the chain whirring as you would expect but no change to the tappety sound. I have since re-adjusted the chain to spec. I would have expected a lot more damage to the tappet guides if they were the cause of the noise which has been there for as long as I've owned the car (6 years/4000 miles) - they would've been severely hammered by now I think. I originally assumed all the tapping was just tappet clearance but this particular noise remained when I had the tappet job done (about 2 years/1000 miles ago). I was told by the mechanic who set the tappets for me, in his opinion, the remaining noise was "a guide". I was unsure at this point whether he meant a tappet guide or valve guide. He is no longer around so I can't follow up with him.

Pete

[MaroonV12]

I bought the kit from XKS, as far as I can tell the quality was very good. Very good finish and heavy for the size ("machine steel").

http://xks.com/i-6917479-17-1580-hold-d ... uides.html



Here is how I installed the kit in my '61.
http://etypeuk.com/forum/viewtopic.php?t=5517

I cant get the link to work and I need to fit a hold down set. Can you please provide a link to your installation process?

[MaroonV12]

Hi all,

I've just been reading Alan Cochrane's recent post re noisy tappets. My 3.8 has a clatter at idle that builds then disappears repeatedly. When the engine is started cold it is silent but gets noisy as it warms up. When cruising I can here this clatter on a trailing throttle (it is a more constant clatter at higher revs) and it is less obvious when accelerating. I am running Penrite 20W60 oil. I had the tappets shimmed and upper timing chain adjusted about 2,000 miles ago by an experienced independent Jaguar mechanic as he had access to a shim kit. This quietened the constant chatter down but this noise that cycles in and out is still there. In his opinion it is a loose tappet guide. I am going to remove the cam covers for inspection and will recheck the clearances and chain adjustment. I assume if a guide is loose there will be obvious signs. Perhaps I should invest in a stethoscope to try and pinpoint the noise before dismantling. As always any advise would be appreciated.

Cheers
Pete

I have a similar problem. Did you ever confirm the issue and resolve it?

[peters3103]

No, still tapping! I also had lower timing chain noise which was caused by the chain tensioner being jammed. That is now resolved but after re-checking the tappet clearances, I’m convinced my noisy tappet is due to it being worn and rocking in the guide. At some point the head will have to come off to have the guides machined and new tappets fitted.

Pete

[christopher storey]

It is the bucket tappets which need replacement, not the tappet guides. This can be done without taking off the cylinder head. But it does require the removal of the camshafts

[peters3103]

Do you think it’s feasible to replace just the tappet buckets without machining the tappet guides Christopher? I had considered doing this before pulling the head off but was advised by a few that machining the tappet guides and fitting oversized buckets was good practice. My view was to take a punt and try fitting new buckets first at much lesser expense.

Pete

[peters3103]

Also, any recommendations for suppliers of good quality tappet buckets and should I be buying the long skirt items?

Pete

[mgcjag]

Hi Pete....if your going for a "punt" and just replaceing the tappet "bucket"....then as mentoined previously when they wear they go barrel shaped when viewed from the side and measured....a solution is to use longer the "long skirt" tappets to replace your existin.......in the existing guides......this is a known often used workaround....i done it myself in a few "tappeg" engins and it has solved the problem....they are available off the shelf by the usual suppliers......Note you will have to recheck the tappet shims when you remove the buckets....and use a torque wrench to refit the camshaft bearing caps......while your in there its worth replaceing tne camshaft bearing shells....overtightening the caps can affect the tappet gaps ..Steve

[peters3103]

Thanks for the advice Steve. Yes I’m aware of the long skirt tappets after discussions on the forum previously. Any manufacturers better than others or do all the usuals supply the same product as is often the case? Rob Beere perhaps?

Pete

[mgcjag]

I used long skirts from SNGB....they worked...dont know if there is a "better" or "worst"......Steve