tapping sound from my engine

[lesliehedley]

Yesterday my 400SE started to produce a loud tapping sound from the rocker covers. It sounds just like a loud tappet. I know there are quite a few threads on here that reckon this is normally a leaking exhaust gasket. My problem is that the engine is running rough as well. It doesn't feel down on power and it's not a definite misfire - yet, but it sounds as though the tappet type noise is in sync with a roughness in the exhuast note. I wouldn't have thought a leaking exhaust gasket would affect the smooth running of the engine. Would it? Any ideas what it might be if it isn't the exhaust gasket? TIA

[streaky]

It might well be a tappet. This and "worn tappets" below it is worth a read

Streaky

>> Edited by streaky on Saturday 5th June 07:10

[father ted]

Could it be a stuck valve/broken cam lobe/lifter etc?

[nick heppinstall]

Hi Leslie. Get a pice of 4x2 ( or similar ). Put one end on your rocker covers and listen to the other end. Try this around the engine where you think the noise is coming from. Of course WATCH OUT !! for any moving parts so be careful !

This should help you to locate the noise. If not at least it will give the neighbours a laugh.

[2 sheds]

does sound like sticking valve, could also be loose spark plug, worn cam or rocker gear wouldn't normally cause obvious bad running.
Tim

[lesliehedley]

Finally got this sorted at my local garage. Itturned out to be one of the rocker arms. There appears to be a cup at the end of the rocker arm where the pushrod fits. This is not an integral part of the arm and the pushrod had worn right through it so the pushrod wasn't lifting the rocker enough. Hence the valve wasn't opening and that caused the rough running. One new rocker arm and all is well again. This is a new one on me. I've never heard of anything like this happening to rocker arms before. just thought you'd be interested.