I just finished a project of replacing the motor mounts, trans mount and replacing the oil pan gasket. That's it. I had to unbolt my headers to move them out of the way to get to the mounts. I finished everything last week and bolted the headers on and filled the engine with oil yesterday. Today I attached the exhaust to the headers which was the last step before starting the car. I started the car and hear this horrible metal on metal rattling sound. I turned the car off real quick after I realized the sound. I checked all around the engine accessories and the fan to see if anything was interfering. I double checked all the header bolts to make sure they were tight thinking it might just be a bad exhaust leak. Then I double checked that I had put the plug wires back on correct. I tried to start it one more time and the same horrible sound was there. I pulled the dipstick to make sure that the oil pan was full and it was.

The only thing that stands out as a little off is that when I pulled the headers, I placed all the bolts in my little magnetic tray. When I went to put the headers back on, I was one bolt short. I just assumed that I had dropped it and it had been cleaned up with the rest of the tools and misc. bits from working under the car. Now I fear the small possibility that I may have dropped a bolt into an exhaust port.

What and were should I start checking to find my problem?

 

You said you checked the fan and that's OK, could it be the clutch inspection cover? PG.

 

That's a great thought. When I dropped the oil pan I had to create a thread on how to get it out. Turns out there was a little tab from the inspection cover that was under the oil pan lip. I pushed it back with a screw driver. I will check that tomorrow to see if I pushed it too far back.

 

A friend at work suggested that if a bolt had fallen into the header while unattached, it would make the same kind of racket I'm describing. Has that ever happened to anyone?

 

When changed my headers last month, the a/c compressor belt was situated at the outside of the metal shield at the lower compressor bracket. Check this if you got A/C.
Terrible sound..

 

I had the same noise. Turned out to be the flexplate/converter cover rubbing the flexplate.

 

i think you answered your own question...that bolt is either in the bottom of your header, or somewhere you really don't want it to be.