I have a 91 Camaro, 305. New engine, just put on Edelbrock TES Headers. I took off the A.I.R. System and plugged off the air tubes on top of the headers. I get a squeeking sound coming from the exhaust. I can hear it plain as day when I get under the car. It is loudest where the two sides join into the single pipe. It doesn't make sense to me. Also, I do not have a Cat and I am running 3" all the way back to the Flowmaster.
The sound it makes is in conjunction with the engine RPM's. It is not a constant noise. It is like something rubbing. It will do it on first start up when cold in park. Once it warms up then it will not do it in park. I have to have it in gear, and then it only does it under load. I can be cruising along on the gas a little bit and it will make noise. If I let off of the gas just a bit then it will quit. I originally thought that it was coming from my tranny. I disconnected the flexplate from the converter and it wouldn't make the noise. Once I hooked it back up then it would do it. I had the tranny rebuilt and still does it. Talk about frustrating. I am grasping at straws here. Anyone have any ideas, please let me know.

Thanks,

R.S.

 

You took off AIR - but did you remove the smog pump?

 

 

Maybe the vacuum line running to the EGR valve?

 

I took off the pump that is driven by the belt if that is what you're refering to.
I took my car into the Chevy dealer and had a Tech look it over and they checked all of the vacuum lines. This is the craziest thing!
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It is not a sucking noise. It is a squeeking noise that corresponds with the engine RMP's. Squeek....Squeek....Squeek... You get the picture. It's not constant.

 

OK - I'm going to guess a pulley then. Get a stethescope and check each moving part. A big screwdriver (long) will work too, or the antenna. Place the sharp end on the housing to a moving part (such as the idler pulley), then rest your ear on the blunt end - the screwdriver will transfer the vibrations to your ear drum, and you can pinpoint the noise to a specific part. When you find the sqeaker, it'll be really loud in your ear. Try that - I've traced many noises with a big ole screwdriver.

 

Guess again. Placed a stethascope all over enigne. Loudest when held to the exhaust pipe hooked to the headers. How would a squeek transfere from a pulley to the exhaust pipe anyway? I've never heard of that before.

 

Sorry - forgot this was exhaust related - guess that means I was exhausted when I replied lol.

OK - I'm guessing you checked for holes in the exhaust. What about where the cat used to mount to the tranny? Since cat is gone, what was substituted for a mounting bracket? You basically disconnected engine from tranny, and noise stopped, so maybe it's a vibration being transferred though the drivetrain and affecting whatever holds your exhaust in place where the cat used to mount to the tranny tailshaft.

Other than that, I'm outta guesses - but will still dedicate a brain cell or two (if I can find one).

 

I have had the cat off of the car for the last 10 years and had no such problems. The cat was mounted under the passanger seat and there was no brackets holding it there....... maybe, it has been 10 years. I will try securing it temporarily and see what happens. I do notice that it does move a bit when the revs are up. I hope that's it. I'm tired of tossing and turning at night trying to figure it out. I certainly appreciate all of the input and ideas that you guys are giving me though. As soon as this is figured out I will let the world know. But untill then, keep the ideas coming please.

Thanks,

R.S.