Intake Noise

On my second 97 Riviera S/C. The first One had a mild case of the whistle, flutter, rattle intake noise when cold. It had the stock intake box so I could live with it. The one I have now has a CAI. When the engine was cold it was very loud, very annoying. I finally got fed up with it. I found that all of my noise was coming from the passage that routes air thru the IAC. The passage can be accessed via a pressed steel plug on the top side of the throttle body. (CAUTION) Be very careful with the following, you don't want metal fragments in your supercharger. I used a point punch to put a hole thru the plug. I screwed a sheet metal screw thru the plug and used it to pull the plug out. The passage has a couple of 90 degree turns in it, makes a good whistle.  The junction between the vertical and horizontal passage is a sharp turn with a lip left from the casting process. I stuffed a small rag in the vertical passage to catch chips. I took a Dremel tool with a round bit and ground off the lip and rounded the edge. With a small hose (aquarium tubing) hooked to my vacuum cleaner. I cleaned out all the residue from the grinding. I repeat all the residue. I used the sheet metal screw with some silicon to plug the hole I made in the steel plug. Reinstalled the plug. Noise is greatly reduced, probably by about 75%. Was well worth the time and effort. You just have to be careful not to leave anything that can be ingested by the engine.

Thanks, Roger. Interesting solution. As for the rattle when cold, do you still hear this? Usually we find this noise is from a worn supercharger coupler. You can read about it here:

https://rivperformance.editboard.com/t3009-faq-supercharger-noise-bad-coupler

I had the coupling rattle also, replaced coupling, fixed that. The intake noise is hard to describe, whistle, flutter, rattle is only close. If you start the engine with the CAI or the air box disconnected you can really hear the noise. This was how I narrowed down where it was coming from. It went away when the engine was warmed up because less air flows thru the IAC. Got louder when the A/C was turned on because more air goes thru the IAC. Also if you blip the throttle the sound would stop briefly, I figured this was because no air was flowing thru the IAC. I have listened to a few other L67 equipped cars with CAI's, some have less noise than mine on a cold start, some have more.

I believe I have the same noise on my '96 3800 Camaro. From the reading I have done, I think the noise might be coming from the EGR where it circulates back into the intake. Not sure if its normal as I dont have it on my '95 Series 1 S/C Riv. Kind of sounds like the throttle body is sucking in rocks with intake tubing removed but is barely audible when put back together. Only way I can think to test is to disconnect EGR at manifold and find a cap with the right threads to seal off at the exhaust manifold. Just be careful removing the EGR piping if you try this, it can kink and tear the piping if you force it off.

How did you get that screw to pull the plug out. I've tried this method using a bolt and a big washer (kind of like the S/C pulley remover), and it just doesn't come out of there. That plug is in there so tight that the screw pops out before the seal gives. When you put the screw in there what do you use for leverage to pull it out. And hopefully we're doing this with the TB off of the engine since I'm trying this on spare parts I get from the junkyard.

Best way I've heard the sound on a cold start described as it sounds like a shop vac for the first few minutes. Especially if you have a cone filter.