Valve Clearances

[oldtimer]

Hi Tintin,
Further to our conversation today I have just checked in my XJ6 Manual and it confirms that both Inlet and Exhaust clearances should be set to 0.012 - 0.014 thou.

These clearances are significantly larger than earlier XK engines

Thumbing through the Manual I also came across a description and operation of the AED choke device , along with an excellent exploded view

Hope that helps

Oldtimer

PS Jaguar Service Manual Publication No E 155 Dated1972

[Tintin]

Thank you for the info OT.

Following our lengthy conversations re thermostats, temperature senders, thermistors, coolant additives at al - on the way home yesterday we got stuck in a long jam on the M40 behind an accident near J10. The car didn't like it at all, overheated, blew a bit of steam and juddered to a halt. Ten minutes on the hard shoulder with the bonnet up in that bitingly cold North wind lowered the temperature enough to re-start and limp to Cherwell services - only half a mile further on - where the car cooled off and we warmed up with a burger and tea.

I suspect the viscous coupling on the radiator fan, which on examination when we got back was free wheeling with negligible resistance with a fully hot engine (in forward motion the temp is fine).

Another job to add to the growing list and todays intention to re-adjust the AED mixture to try and prevent stalling under load when cold. Ah - the joys of Jags!!

Robbie

[Tintin]

Back to valve clearances.

I attach a table showing the clearances I measured last month and, for a more complete picture, a table showing the cylinder compressions.

I am inclining to the view that I will adjust the clearances if that can be done without removing the head (it may prolong the life of the valves/seats). If the head needs to come off I will probably wait until a valve/seat fails and then strip the head for a complete overhaul.

Can adjustment be done with the head in place? Any views on my measurements/intentions welcome.

Robbie

PS I am finding the process and limitations in uploading images and documents most tedious - hopefully the new site will be user friendly.

[mike020150]

Bearing in mind the accuracy limitations of most compression testers, I wouldn't be concerned about the absolute values. Whilst they are not equal, the values are all within 10% of one another which is reasonable. Unless you are hell-bent on enjoying the 'pleasures' of tappet adjustment, I'd leave well alone for the time-being. Did you carry out a 'wet' test to establish if the possible slight loss of compression (if it exists) is valve or piston related? Also, it might have a bearing on the outcome of a tappet adjustment, i.e. any issue might be piston related and not a tappet problem. Mike.

[piman]

Hello Tintin,

personally I would adjust those, Yes they can be done in situ, just do not rotate the engine while the camshaft is removed (I know, why would you?). Tight clearances are more likely to cause valve problems than loose ones.

Alec

[Tintin]

Thanks both.

I must confess, a wet test didn't cross my mind - I jumped to the immediate conclusion that the result showed general mileage related cylinder wear rather than a particular problem as the compressions were reasonably well grouped. Having said that it will be easy to do and will confirm the assumption (or not!).

Robbie