XK timing chain rattle on a 1968 car

[pixieporsche]

Tell me more!

4.2litre XK, 1968.

Is it purely a case of "it needs adjustment" or is there more than meets the eye?

[jith]

pixieporsche said:

Tell me more!

4.2litre XK, 1968.

Is it purely a case of "it needs adjustment" or is there more than meets the eye?

If you have light, almost musical tinkle when the engine is idling, but then disappears as you open the throttle, it is the top chain that needs adjustment. You access the adjuster throught the breather outlet on the front of the cylinder head. You should have a special tool to do it, but it is easy to make something up.

Strictly speaking the correct procedure is to remove the cam covers and reset the valve timing when you tension the chain, because the act of tensioning it will revolve the cams towards one another, but if it is only a small adjustment, it shouldn't make a huge difference.

If you have a harsh rattle at idle that persists even when the revs are raised, the lower timing chain tensioner has failed and dropped into the sump. This is most unusual in the old XK engines, but does happen on high mileage, neglected cars. If not repaired promptly the chain will break: bye, bye engine!

J

[pixieporsche]

Thank you, suppose I better go and have a look at the car and have a listen!