Cams and clearances

[Gelbster]

Suggest you 'search' this issue.
1. The lifters were revised and an update part # given. Nobody knows what the change was.
2. The lifters that do not 'spring back' - are they jammed ? The tappet is in two mating pieces with a spring inside and a little circular retainer. So you mean the two halves of the tappet are jammed together?
I chased this issue hard recently .The tapping was not the full extent of the problem. A rod bearing was beginning to fail.A feint lifter (or so I thought) noise that over a few days got louder.BTW several of my lifters were jammed also.
Cut open you oil filter,drop the pan ,check your mag drain plug ,fit an LN Filter .
I am experimenting with BMW lifters because they were a fraction of the price.More if you search.

[jsceash]

I have researched. You may try 99610504172.They supersede the others no real difference. This was mostly because the 2005 and 2006 987.1 engine they change all the number but many of the part are the same. Dealer show number superseded

I used an electronic stethoscope the noise was coming from the intake side of cylinder 4. Also where I found the tappets that do not pop back they are compress continuously at least while cold. I did notice that once the engine was hot the sound became less noticeable so I plan to steel my wife's electric fry pan and do the hot cleaning suggested. I may still replace them all anyway.

The sump was spotless and the filters have been clean since the first oil change after I rebuilt the engine and run in March 2013. The only things not replaced at that time was the cams, Lifter (tappets) and Tappet housings. I should have replace the tappets.