Anybody changed this? I wanna know if it's a bitch to do really, i'm getting tapping from my lifters and hoping this might shut them up.

 

does the chatter only occur when the engine is cold?

 

Cold for a few moments and then once it's hot, after a good hard drive.

I'm thinking retention valve is clogged up and not shutting fully so the pressure is being lost, or the oil pump is packing up, but no pressure light on.

 

Particularly if the noise occurs only on idle, it sounds like oil starvation of the cam chain adjuster, caused by leaky cam seals (if you are lucky; been there ... done that) or sludge buildup (if you are unlucky). Can you isolate the noise to the back of the cylinder head?

 

No it's coming from all over, mainly the middle of the cam. I'm going to run a pressure test on it first then go from there.