Valvetrain tapping sound?

[davida1_hiwaay_net]

Been living with this tapping sound in my engine for a while. It has recently got a little worse so I want to fix it. I listened to the engine through a piece of hose and can isolate the sound to the rear bank towards the top of the engine. The sound is at 1/2 crank speed, only noticable at idle, and it does not matter if the engine is warm or cold.

After taking the valve cover off, all the rockers are still adjusted equally, nothing looks to be bent or out of whack. Each pushrod moves equally as the starter cranks the engine and oil comes out of all rockers.

The engine is a 2.8 MPFI from a 1985 Cavalier Z24. Has iron heads.
Here is a video of the engine idling posted to YouTube.

One reason I want to figure this out is because I'm commuting 5 hours every 2 weeks in this car and don't want to have an engine failure on the road somewhere in BFE.

Any guesses? Thanks in advance!
David

[davida1_hiwaay_net]

Well - I took the rockers off and found some problems but nothing like what I would expect to cause this strong of a tapping sound. The #1 exhaust valve stem tip and rocker are wearing abnormally, see below.

Wonder if this rocker could cause such a sound? When pushed down manually, all valves feel the same, none move side-to-side, and all make the same sound when released.
Thanks,
David

[BoostED00GagT]

hm, weird, that sounds more of a harder part making noise...uppervalvetrain noise is more like a taptaptap...not a knockknockknock...i cant really see in the pic...does it lok to have some bad wear?

[davida1_hiwaay_net]

post deleted

[davida1_hiwaay_net]

Just lost my reply, damnit! Anyway I replaced the rockers and adjusted them. Got rid of some minor clatter but the knock is still there.

Engine was rebuilt and turbo'd 120,000 miles ago and developed this noise about 10,000 miles after the rebuild. I have a feeling it is a piston.

I have one engine apart for a rebuild and don't want to get 2 going at once! This one is next in line. It has earned a rebuild! In spite of the knocking it will pull 13 PSI boost without complaining. Has been a blast to drive and made alot of rice boys very very sad!

Ordered a set of roller tip rockers from Comp and they arrived in a sealed box. In this box were 12 rockers, 12 nuts and EIGHT rocker pivot balls! They overnighted the 4 missing balls to me, for free no questions asked. It is frustrating to get an incomplete kit but their customer service is second to none!

Will post what I find when I tear this engine down. It needs a roller cam when it goes back together - I may get a later model block that has roller lifter provisions. May cost less than a retrofit roller cam!

Thanks,
David