Have a 1993 Silverado I have had for about 5 years, Wife drives to work daily. We totally Love this truck but we have a problem no one can resolve so far.
Driving about 50 MPH starts a clattering or rattling noise from under hood.
I have had this checked out by several good mechanics and also Chevy dealership and no one can find the problem.
It almost sounds like you are running cheap gas in it, but I have tried several brands of gas, and octane boosters and that doesn't help.
It could be something under the hood that is loose, but I don't know what.
Anybody had this type of problem with a 93?

 

Sounds like detonation..need to retard timing just a little.
detonation is when...before piston gets to top dead center ..timing fires it down.
The way fuel is these days ...about have to retard some.
Just loosen distributor..turn clockwise just a little tighten back take for a drive.
Need be adjust a little more.

 

I believe on 1993 and newer engines the spark timing is controlled by a control module using info from various sensors and is not adjustable.

 

I'm also having similar sound in my 1993. The truck runs a lil rich and at times you can feel a boggle. The sound comes out when the engine warms up. on a cold start you cant hear the sound. Let me know if you resolve this problem, thanx.