Top end tapping - still

[peters3103]

Hi gents,
We’ll after having my engine out to address timing chain and tappet noise I was disappointed to discover after refitting it I still have a tap tap tap in my engine. The lower timing chain noise was caused by the tensioner being jammed (no shim fitted so jammed when bolts tightened) This was fixed along with the tappet clearances being checked & adjusted. The water pump and crankshaft damper were reconditioned as well. All done by a very experienced, reputable Jaguar repairer. (I gave him just the bare engine) I refitted it in November, a year after removal, as in the meantime I also attended to some paint issues on the frame and refurbished the front suspension. The repairer agreed after listening to the engine (in my absence from a cold start up in my garage) that the tapping was a little excessive and offered to recheck all the clearances. They were found to be ok. He noted that it has S3 XJ6 camshafts fitted, which operate with wider clearances, and along with 3.8 cam covers would produce louder tappet noise?? I took this on board and arranged to collect the car. Unfortunately he was not there to speak to when I did as he had gone to hospital to have surgery. On the drive home (200 miles) I noticed, after the engine was fully warmed up that the tapping was still quite noticeable. More so than before? Maybe. I’ve since spoken to him again and asked if the car was driven by him to get it up to full temp but unfortunately he hadn’t. I’m certain that the tapping becomes noticeable once the engine is hot. It’s doesn’t really seem consistent and comes and goes depending on engine revs and load. His recommendation is that the cylinder head will need to come off for a proper inspection and repair. I suspect he is probably right. I note it has had the tappet guides secured in the head before my ownership so that’s not the problem. The engine seems otherwise ok. Runs well, good performance, minimal oil consumption and approx 50psi indicated oil pressure at 2700 rpm hot. I’m determined to get to the bottom of this as it’s been an issue for many years and miles now. Very frustrating.

Cheers
Pete

[mgcjag]

Hi Pete.....were the tappet guides and tappets replaced.....or was it just re shimmed.......I would question that a S3 camshaft with wider gaps causes louder tapping. .not in my experiance.....do you know what gaps inlet and exhaust were set to?.......if your capable then pull the camcovers and check the gaps yourself.......Iv have experiance of an engine tapping loud after a rebuild by Jaguar themself.....the gaps were all wrong...most had no clearance at all....Steve

[abowie]

Hi Pete.....were the tappet guides and tappets replaced....

Beat me to it.

[christopher storey]

Just to amplify the pooint about tappets and tappet guides : as the guides wear, the clearance between the sides of the bucket tappets and the guides tends to increase, but much more importantly ( because wear is usually minimal ) over the years the buckets themselves have a tendency to become barrel shaped . They then rock in the tappet guides and create noise with each valve opeining and closing

PS It is extremely unlikely that using later camshafts and the appropriate 12 to 14 thou clearances will increase noise - the change to these parabolic cams was made in order to reduce noise

[peters3103]

Hi, thanks for responses.
No nothing was replaced just the clearances checked, adjusted and then re-checked 12 months later after engine reinstall and start up.
It would surprise me that my repairer wouldn’t have checked everything visible with the covers off for wear - particularly the second time he had the covers off. My level of experience in this area is minimal so I wouldn’t really trust myself to make a diagnosis. I’m sure the clearances would be right. I’ve had them done 4 times by three different Jaguar mechanics over the years but the tapping remains. I don’t think any of them have driven the car long enough and got it warm enough to hear it. From past XK engined Jaguars owned and listening to others cars I’m absolutely certain it’s noisier than it should be.

Pete

[mgcjag]

Hi Peter....I would be more scheptical that its been done correct. ....your guy has already in my opinion made excuses.... (noise due to cams and cam covers)........either check yourself its not difficult or send it back and ask what gaps were set.....does your guy know the difference in the 3.8 cam gaps and the 4,2 gaps....Steve

[malcolm]

Pete, might be worth recording the noise when hot and posting on here so people can hear and make a judgement.

[peters3103]

I’ll give the recording a shot Malcolm but from past experience even lovely quiet engines sound like a barrel of bolts when recorded. I’ll do one on cold start then fully hot after a drive for a comparison.

Pete

[malcolm]

Sounds like a good idea. It's surprising what some of our experts (not me BTW!) can tell from a recording. I posted a video of my newly refurbed engine running, to sort of boast, only to be told (correctly!) by Christopher that my fan belt was too loose.

[peters3103]

Steve, yes he noted the 4.2 S3 cams when he had the engine the first time so set the clearances accordingly. I think his only error was not getting the engine hot and listening to it then as it sounds ok cold. I’ll cut him some slack here as he was poorly and heading to hospital for surgery and also in the middle of organising moving his business.

Pete

[peters3103]

Sounds like something I’d do Malcolm! I was so pleased with my achievements with regards removing/replacing the engine and rebuilding my front suspension along with much detailing. Very disappointed when my engine was still noisy as it was the catalyst for the whole job really.

[PeterCrespin]

Piston slap is worse cold and gets milder as the engine warms, but potentially the pistons may have been installed back to front, causing some unusual noise level? I've never heard of it but 4.2 pistons often have offset pins and an indication (either an 'F' or an arrow ->) which should face the front. Try a stethoscope on the block by each cylinder for thrust face rocking or slap (inlet side) and pull the plug cap of as you listen to any resulting changes at idle (small ends?).

Valves loose in their guides can rattle, but it's not normally a big issue on DOHC bucket engines, as they apply little/no side thrust (unlike a rocker tip wiping across the end of the stem).

If it's tappet or clearance related it will alter by revs but not load. A rod/piston/bore related problem normally varies under load, and don't change much whether hot or cold. Small ends, for example, can rattle on the overrun. Does it smoke under hard acceleration (as seen by a follower)?

[peters3103]

No exhaust smoke evident Pete. I may be wrong about the tapping being worse under load - it just taps all the time when hot really, increasing with revs. I’ll have another good listen all over with my stethoscope when I’m motivated. I seem to have issues with all my cars at present! I’ll certainly have a close look at the tappets and guides for signs of wear. Thanks for all replies and for your informative chat too Andrew.

Pete

[Nieman64]

Peter, just thought. I had a top end sound years ago. Checked valve clearance several times, still noisy. I described it to my dad and the first thing he said was a loose valve seat. Pulled the head and sure enough it was the valve seat. All from a description on the phone. He just turned 89 two weeks ago, Still the smartest man I know.

[peters3103]

Peter, just thought. I had a top end sound years ago. Checked valve clearance several times, still noisy. I described it to my dad and the first thing he said was a loose valve seat. Pulled the head and sure enough it was the valve seat. All from a description on the phone. He just turned 89 two weeks ago, Still the smartest man I know.

Thanks for this. Yes a valve seat had been suggested but would it have run for the last 10000 odd miles without letting go? I’m not sure. The head will have to come off in any case so all will be revealed.
My dad too was always very helpful with good advice but sadly not with us anymore. You’re fortunate to have the smartest man you know still around. Cherish it.

Cheers
Pete

[Steve1967]

Hi Peter, I just posted with a similar problem and related questions however....

I had one valve that was very noisy. The reason was that I had a new valve seat fitted and it was not properly ground back to factory tolerance by the engineers, so the valve sat lower in the head. Only by 20 thou, but this meant that the shim at the other end was sitting in its recess in the spring cap, but was NOT in contact with the valve stem. Consequently, the spring was slightly compressed (by 20 thou) every time before the valve even moved causing a hell of a racket, despite the valve clearances appearing to be perfect. Essentially a 34 thou gap in two parts!! Like you, I have XJ6 Cams.

It was a Jaguar mechanic I chatted to at Thruxton last weekend who suggested this.

Its easy to check on all but the front cylinder by removing the cam bearing caps and lifting the cam gently, without straining the chain, remove the buckets (a magnet is best) and you can then feel the shim resting on the valve top. you can slightly rock it all around. If you cant, check with a depth gauge to the bottom of the step holding the shim to the top of the valve stem. Be careful not to mix the buckets up, they need to go back in the same hole. Do just one at a time.

Now wanting to remove the head, my cure was to fit the thinnest shim I had, put a blob of weld in the middle of it where it touches the valve stem, and grind that flat. Keep adjusting this until you get the correct thickness where it rests on the valve stem and with the 14 thou gap. I then found a shim the same overall thickness and ground a step around the bottom edge of the shim allowing it to be in contact with the valve stem, thus preserving the case hardening, so the shim is like an up side down top hat. Its a pain with multiple refits of the cam, but it worked for me on this particular issue.

I hope that helps? PM me if you want more details.

Regards

Steve

[abowie]

Its easy to check on all but the front cylinder by removing the cam bearing caps and lifting the cam gently, without straining the chain, remove the buckets (a magnet is best) and you can then feel the shim resting on the valve top.

Regards

Steve

Steve are you saying that you managed to remove the buckets without disconnecting the cam sprocket (and hence the chain) from the cam? I'm guessing you have the cam higher at the back than the front and loosen off the chain tensioner?

[PeterCrespin]

I had one valve that was very noisy. The reason was that I had a new valve seat fitted and it was not properly ground back to factory tolerance by the engineers, so the valve sat lower in the head. Only by 20 thou, but this meant that the shim at the other end was sitting in its recess in the spring cap, but was NOT in contact with the valve stem. Consequently, the spring was slightly compressed (by 20 thou) every time before the valve even moved causing a hell of a racket, despite the valve clearances appearing to be perfect. Essentially a 34 thou gap in two parts…

It was a Jaguar mechanic I chatted to at Thruxton last weekend who suggested this.

Now wanting to remove the head, my cure was to fit the thinnest shim I had, put a blob of weld in the middle of it where it touches the valve stem, and grind that flat. Keep adjusting this until you get the correct thickness where it rests on the valve stem….

I have to say this is dangerous advice and in some respects simply wrong. Someone may lose an engine in extreme cases due to a dropped valve, so pardon me if I come off as dogmatic or pushy or whatever.

No matter what depth the new valve seat was fitted or ground to, it will NEVER alter the depth of the valve in the spring collar. All it will do is alter the shim size required between the valve tip and the cam base circle. The ONLY ways you can get the stem sitting below the level of the collar recess are:

1) A faulty valve (too short above the collet groove) - usually because of grinding the tip to compensate for sunken seats/worn valves.

2) A faulty valve spring retaining collar - due to incorrect manufacture or damage from coil binding in a non-standard setup. I have seen the tapered split collet hole wear oversize on custom alloy spring collars used with strong springs and racy cams but haven’t seen it with steel collars and stock valve gear.

3) Faulty split collets allowing the valve stem to sit deeper or higher in the collar. The most recent example was an almost invisible ‘dent’ in the wider upper surface of one collet - possibly from being punched or tapped into position during valve installation. This tiny bruise ‘widened’ the thick end of the tapered collet enough that it didn’t slide as far down into the collar, which meant a thinner than usual shim, which was in danger of jumping out of the collar recess. The cure was to dress the collet back to its proper shape until it wedged cleanly at the right depth with the valve tip protruding a little less (the opposite of your need in this case).

Even if an engine with a ‘modified’ valve assembly starts and runs OK with a valve sitting too low in the collar, the day you miss a gear it could end in tears. The way to fix a shim that does not rock on the valve tip is a new valve, or in rare cases a new collar or split collets.

[tinworm]

Peter Crespin is quite right in what he says.
I have an XK150 head on the bench now and it has suffered a lot recently - at the hands of a local engineering firm. Not to go into a long story on this head - 2 sets of valve seats later- I ended up buying myself my own American made (ie Quality ) valve seat cutting tool (hard seats now - so old tools wont do) just so I could get the seat height right. There is only 25 thou of adjustment in the standard shims so the seats must be cut perfectly to set the valve in the middle /top of the shim range . This has now been possible.
Not the case with my head but others may want to take care when a engine machinist wants to recut the valve seats "as a matter of course" - you could rapidly find you cannot find a shim to give you a factory valve clearance and there are only two things you can do to give that back - shave off the top of the valve stem or replace the seat with a new one. You don't need to be Einstein to see which one is a bodge and which one is the correct approach.
Steve - you may need to lift your cylinder head and deal with this problem for peace of mind - I would.

Barrie

[peters3103]

Sound advice here as usual. I’m certainly going to remove my cylinder head and have it sorted properly once and for all. Just a matter of waiting for some motivation, warmer garage weather and a replenishment of E-Type funds.