Please help! My engine is making a loud rattling noise. Two weeks ago i was driving to my friend's house and thats when it started. I had good oil pressure but was low almost 2 quarts. I topped if off and it kept doing it. I took the valve cover(noise was coming from the passenger side) off. The rockers weren't loose and nothing looked out of place. My friend told me to run it without the cover so we could see if anything was broken. After a while it stopped. I put the cover back, drove it for about a week. Now its back. It's not a pinging or knocking but more of a loud rattle. The oil pressure and level are fine. My boss told me to change the oil and add some CD2(some additive), cause I could have a stuck valve. That didn't work. I'm thinking it's a lifter. Any possibility it could be some major engine component. Oh yeah, I forgot to mention that it's not doing it all the time. For a second or two at idle it's fine, but most of the time it's rattling. And i found out it affects my idle, my tach will move down slightly and my belts also slow down then goes to normal.
Please help, any suggestions will be greatly appreciated.

 

How loud the the rattle? Is it TPI? In the past with TPI I have found that noise from the valve cover could be coming from the oppisite side of the problem. Remember, the left runner feeds the right side of the motor and right feeds the left. If it's real loud maybe a main bearing??? It could be a million things, need more info to find out.

 

It's carburated. It is preatty loud. Parked on the side of my street i can hear it inside my house. It's louder than my exhaust(flowmaster). What is wierd is that it's not constant. Why would it stop for a short 2 seconds then come back. Also last week when it started why would it go away when I added the oil. Before I changed the oil, if I added some it would stop then come back once I revved it. It was already full though, so I didn't want to add any more.

 

Water pump? Fan clutch?

Try a piece of heater hose stuck in your ear, and probe around everywhere with the other end until you find where it's coming from.

 

Did you check the shields on your cat? They are nice and loud when the welds break! And the sound will come and go depending on engine rpm and how they get shifted around. If the shield is loose just remove it. I ahve been running with out it for 2 years with no probs.

 

It's not that. It's welded up preatty solidly.