Hi, I'd appreciate any input anyone has on this. While driving the other day, I noticed a tapping coming randomly from the engine. I pulled over and listened, and it sounded like something banging on the valve cover from underneath.

I take it home and take the valve cover off (I needed to replace the gasket anyway, actually). Everything seems fine. I turn the motor over , and there's no noise, and everything looks correct. I take off the intake man to see if something's caught in the valves, and they're clear, so I actually hook the coil back up and hang it from the hood and have a friend start the car with the valve-cover off. The noise starts immediately, and seems to be coming from (and this is an educated guess based on what it sounds like) one of the #1 piston intake valves. It's sporadic, not constant, and it's not timed to the firing order at all. It happens more often when you rev (to the point where it's nearly a constant sound), and stops when you let off the gas until it starts idling again.

I have noticed no performance issues, and the engine doesn't run any differently. I have just rebuild the engine, and reassembled about a week ago. Bored .020 over, JE 8.8 pistons and rings, new bearings, new gaskets, etc. Both the head and block have been decked and cleaned up at the machine shop. Compression test comes up straight 185 across the board.

Any suggestions as to what it could be or what I could do to figure it out?

I posted rather late, so I figure at least one bump is in order. ;)

that apparently is totaly normal for our cars mine has done it for years now with no major problems.

When I say "noise" I mean... "loud noise".

Imagine, if you will, putting a marble in a paint can and putting it on one of those automatic shaking mixers. That's about what we're talking about here.

It always made a little noise, but -nothing- like this.

Try a compression test.

Originally posted by eclipse_99rs
Try a compression test.

To quote my original post:

Originally posted by RyMon
Compression test comes up straight 185 across the board.

I took off the intake manifold today hoping that something small enough to fit through the throttle body but too small to fit through the valves was sitting in the #1 runner, but no such luck. The valve stem is straight, and I can't feel anything wrong with the valve itself, nor do I see any evidence that anything is moving around in there where it's not supposed to.

I'm stumped... ideas?

Sounds like the symptoms of a spun bearing to me. But probably not considering you just did the rebuild. Hows the oil? any leaks? Make any hard right turns lately?