What is this noise? (win a prize....)

[Shortcutsleeping]

1993 LT1. Buddies car. All stock. 200k miles. Never any previous problems but this noise has cropped up. Sometimes it does not make it hardly at all, sometimes it is very obvious.

Typically the noise stays there on accel and will stop on decel until it hits the idle and it shows back up. In the video it sounds a little deeper than in person. In person it sounds way too light to be a rod knock (sadly, I know that sound) and we ran the valves last week and checked valve springs. Runs smooth, no SES lamp, good power.

Thoughts?

Noise is really evident at about 25 to 30 seconds in. This is a cold start.
http://www.youtube.com/watch?v=tsWz4s4vrMM

Any help appreciated.

Costas
cars and such...

[GlennCMC70]

dead lifter(s)?

[Shortcutsleeping]

Well, I had kinda thought that, but we ran the valves and all of them came out about the same...

<shrug>

Costas
cars and such...

[j3ffbrooks]

My 96 GT made a similar sound turned out to be the timing chain slapping around because of a bad tensioner. I know LT1 is a pushrod, but 200K miles can stretch out a chain.

[Shortcutsleeping]

Finally took a peek (between rain showers) tonite. Passenger side rearmost exhaust bolt is GONE.

Will drop ypipe and put new bolt in when we aren't dodging raindrops and recheck.

Costas
cars and such...

[AI#97]

If it were a mod motor, I would say rod bearing and write me a check for 4 or 5k bucks!!!