1G Valvetrain noise at 2500 RPM, why?

[er82]

Some background: rebuilt stock 6 bolt head. The head did come with the project car and had warped cams, and possibly bad lifters or stock springs which I swapped out (valvetrain was knocking at idle). So I put in used GSC S2 cams, new GSC lifters, and new kiggly street springs, and new kiggly hla. After like 10 drag passes it developed a valvetrain noise at 2500 rpm, during free rev, or just when crack open throttle at around 2500 rpm. On load it seems to go away and on deceleration its non existent. It sounds like cams smacking the rockers (or could be anything near intake cam side, I'm guessing). Car still runs 12s like before (depending on my launch), and boosts to 29 psi as expected. I replaced rockers with good clean ones, I also replaced GSC lifters with another brand new set, and put back the stock hla. Compression is 145psi on all 4, no flakes in oil, oil pressure seems good. I'm out of ideas of what it could be. Someone said may be stuck valves or possibly bad rebuild. Anyone have ideas?

 

[motomattx]

Sounds more like rod knock or main bearings to me. Are you sure its not an exhaust leak?

 

[er82]

Sounds more like rod knock or main bearings to me. Are you sure its not an exhaust leak?

I think the rod knock would be apparent through the whole rpm range. And there are no metal flakes in oil. I'm quite certain the noise is coming from valve cover as I lean over it to rev it.

 

[motomattx]

Rod knock often sounds like its coming from alot of places, maybe a sound clip would make things better to give an opinion.

 

[er82]

Here is the video. Can hear the noise best on the 3rd rev.

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[motomattx]

That doesnt sound like rod knock, I have heard timing belt tensioners and timing belt pulleys make that sound when they are failing, I have also had bolts holding the timing belt pulleys back out and make that sound, I would look there first, have you pulled the valve cover to check for collapsed lifters? I am assuming that you have.