tappet clearance

[baganz.sven@web.de]

Dear colleagues,

just a short sunday morning workshop question to those with more experience than I have.

Checking the tappet clearance of my E I found that I have between 0.007 and 0.012 in clearance.
On the A bank 5 valves have 0.012in which is minimum as I read.
Because so many are out of tolerance I have to adjust anyway.

So no which clearance would you set?
Can I leave 0.012 an the set all other valves also to 0.012 or should I adjust all to 0.013 (or 0.014)??

I have no experience which clearance is the most appropriate?

Very funny that the pre owner has told me that he has checked the clearance and everything is OK.
Thank you for advice

Sven

[jagwit]

Hi Sven

To leave 5 out of 24 valves, will save some labour, but not much really. Ideally, you should have a large selection of shims to choose from.

I would therefore encourage you to set them all to .013/0.14 as recommended.

Also note the thickness of the shims that you remove from each tappet. None should be thicker than ABOUT 2.8mm (0.110") - this is not a hard and fast rule, just Philip's (moi) guideline. If they are, someone may have shortened the valve stem (probably because of valve seat recession) and you should check for interference between shim and valve spring seat. Ask me how I know this.... Also check for valve guide wear and valve seat recession.

Its a very time consuming job, so be patient. Its also a good time to replace the valve stem seals.

Most importantly though, DO NOT accept that the cam timing is correct. Please get the cam timing tool and check with your own eyes that the cam timing is correct.

[Ole-xke1974]

A bit of additional information on the topic from my side.
I followed some recommendation to set the valve clearances 0.002" bigger than spec, which should increase low end torque.
Whether I have more low end torque or not, is a butt dyno assessment. Maybe.
What I do know is that the tappet noise is more than I want in my otherwise quite refined "sports" car and will set aside a weekend sometime in the future to return to standard gaps.
Important tools to have on hand apart from your standard shop tools are the cam setting tool also mentioned but you will also need the timing chain tensioner release tool.
Good luck and take your time ..... Ole

[baganz.sven@web.de]

Thank you for the comments.
Is the timing chain tensioner retracting tool necessary?
It is not mentioned in the manual.
The cam tool and the JD40 I have.

By the way, there is no temperature mentioned for measuring (e.g. 20°C)
Normally the manufacturer mentiones a temperature.
At the moment there are -2°C in my garage do I won't work on it anyway.

Best regards
Sven

[jagwit]

Is the timing chain tensioner retracting tool necessary?

You don't need it to get the cam sprockets off, I suppose, but you surely will need it , or something like it to release the tension on the chain to be able to get the sprockets back on.

Be sure to release the locking catch on the tensioner BEFORE you start to de-tension the tensioner, and KEEP IT released while de-tensioning the tensioner.

I try to de-tension the tensioner as little as what I can get away with in an attempt to try avoid it breaking.

[baganz.sven@web.de]

Hello Philip,



greetings from Braunschweig/Germany

Sven

[baganz.sven@web.de]

By the way, does anyone have experience with the ambient temperature the Jaguar workshop manual refers to for tappet clearance adjustment??
Sven

By the way, there is no temperature mentioned for measuring (e.g. 20°C)
Normally the manufacturer mentiones a temperature.
At the moment there are -2°C in my garage do I won't work on it anyway.

Best regards
Sven

[jagwit]

By the way, does anyone have experience with the ambient temperature the Jaguar workshop manual refers to for tappet clearance adjustment??
Sven

Sven, I recon you can ignore temperature.

According to https://www.engineeringtoolbox.com/line ... _1379.html, steel's linear expansion is about 0.00011mm per meter per 10ºC. A valve stem of about 150mm will thus expand 0.0000017mm (0.000042") per 10ºC. If my sums are correct?

No feeler gauge can measure that....

[baganz.sven@web.de]

Hello Philip,

for Aluminium cylinder heads this is different.
I just ask because for my actual VW van from 1989 the workshop manual show 2 different values for valve clearance. One is for a "warm" engine, one for cold.

Fortunately it's too cold in my garage at the moment so I will not proceed at the moment.
I will adjust when we have reached 20°C again.

Best regards

Sven

[jagwit]

my actual VW van from 1989 the workshop manual show 2 different values for valve clearance. One is for a "warm" engine, one for cold.

Fortunately it's too cold in my garage at the moment so I will not proceed at the moment.
I will adjust when we have reached 20°C again.

There is NO WAY you will be able to measure / adjust the Jag V12 tappet clearance while the engine is still warm

[baganz.sven@web.de]

Today it was warm enough to start working on the tappet clearance. I found it very easy to take the camshaft out. For the tappets I used a strong magnet. Fortunately there is no wear visible.
Thanks again for your comments. Beeing new to Jaguar the forum is really helpful for me.

[MarekH]

I've never bothered with the chain tensioner tool. Once you have undone the four bolts holding the camshaft sprocket on, you can get it back on just by pulling a bit and if necessary, helping it along a bit with a big long screwdriver down the right hand side. There isn't so much tension in the tensioner that a bit of elbow grease and leverage can get past.

Similarly, unless you want or need to change the cam timing, the cam tool isn't needed either - just don't undo the circlips inside the camshaft sprocket. It can then only go back on one of four ways and if you can't remember where the notch was when you undid it, you really ought not to allowed near a stripped engine.

What you DO need to do is to do up the cam cap bolts to a measured and equal torque using a torque wrench each and every time as the flex in the camshaft (once it is pulled by the timing chain) can pull your valve timing measurements out by 1 or 2 thou because the front end of the camshaft will twist from the pull of the timing chain.

kind regards
Marek

[baganz.sven@web.de]

Dear Marek,

Thank you for your advice. I really appreciate getting such comments because it is the first time for me to work on a Jaguar.
I'm really happy to get your support

Best regards
Sven

[MarekH]

I should add that you don't even remove the sprocket from the chain. Just unhook the sprockets from the camshafts, tie the sprockets and chain up together and hang them up where they are.

You also don't want the distributor rotor arm to be pointing a different way prior and post stripdown. (That's what the jackshaft retaining tool achieves without taking the distributor cap off.)

kind regards
Marek

[baganz.sven@web.de]

Dear Marek,

everything worked exactly like you described.
Only thing I found a little bit difficult was to get the bearing cap nuts back on because it's necessary to compress some valve springs. It should be easier if someone helps.
But finally I got everything back in. Of course I use a torque wrench because I'm always trying to be very precise.
Finally my wife (who also is a mechanical engineer like me) said that this engine is no swiss wathch but "only" an engine.

Only thing I couldn't find in the manual was the tightening torque of the sprocket retaining bolts.
Due to the locking tabs this might not be too important so I will tighten them with 20Nm.

Thank you again for your advice.

Sven