Help me diagnose an engine noise!

[chimchim]

I know this drives you guys nuts, but please forgive me. I've searched numerous sites and I cannot find a similar noise noted anywhere! I have a noise in my engine that I would NOT call a knock. More like a chirp, flutter or maybe a clinking. Not knock. The car is a '97 with 64,000 miles, stock bottom end, PI heads and PI intake. All bolt-ons except headers. The car does have a mail-order tune that's been fine for over a year (in fact all mods have been working fine for over a year). Makes about 245 hp at the wheels on the dyno, so I don't think I've smashed the rods or pistons. Sometimes I get the noise on start up, then when it warms up it goes away. Sometimes, I get the noise only above 3,000 RPM and up. It definitely is contingent on the RPM with it's frequency.

I've been told: it's a bad oil filter, exhause leak, detonation, piston slap or rod knock.

I've changed the oil filter with only Motorcraft, I've checked the manifold to h-pipe bolts and h-pipe to cat-back bolts, I've put octane boost in it to rule out detonation, just in case the tune got screwy somehow or I got bad gas. I've check all the plugs and wires.

The car does not idle rough, or have a miss and it still runs great all the way through the rev range.

Please help me out with this before I pay a mechanic to listen to it. Any help is appreciated.

Thanks!

 

[COramprat]

Noises like that seem to resonate throughout the engine bay making it hard to pin down. It could be as simple as an idler pulley going bad or valve train noise. To eliminate the latter take a stethescope (you can get one at a parts store) or a large screwdriver works too and place the tip on the valve covers. Put your ear to the handle and determine if the noise is actually internal. If not then proceed to the accesories such as the alternater, AC compressor, power steering pump etc. Try to get another person to rev until you hear the noise and see if you can find it's source. Also make sure your crank bolt is tight...I see you have underdrives so you could be getting timing chain noise if the crank bolt had backed out. You just have to use your ear to try and find it and see if you can fix it yourself. Otherwise it's off to a mechanic...

 

[BurningRubber]

Chirp or flutter makes it sound like a throwout bearing possibly.

 

[DTNODYA]

Throw Out Bearing. 94% sure.

Try this: When you've just started it keep the windows rolled up and the air off. Listen and see if when you push in the clutch it makes some kind of sound (almost like audio feedback through speakers ..)

And at idle it could be 'chirping' but when you push the clutch in it stops?