496 HO Whistling at 2000 to 2200 RPM (2002) - Cobalt 240

[TarryKnot]

Hello, I recently purchased a 2002 Cobalt 240 with the 496 HO/Bravo3 package. I have run it for about 10 hours this summer and recently had passengers note that there is a whistling coming from the engine compartment. Only shows up between 2000 and 2200 RPM's, about the right towing speed for tubes and wake boarders. (my kids). The sound increases as the throttle is advanced and then will go away. It sounds to me like a super charger/turbo winding up but this engine does not have one as far as I can tell.

I am new to boating, but was a car mechanic in the old days so I at least know enough to be dangerous. Service center says its "normal". I am skeptical of course.

WOT we hit 5000 RPM and 62 MPH, hard to hear anything at that point!

Has any one encountered this type of noise? Maybe its common to the 496 HO but I have not found anything on it.

Thanks

TarryKnot

 

[NHGuy]

Re: 496 HO Whistling at 2000 to 2200 RPM (2002) - Cobalt 240

I'd bet it's intake noise. My 350 has a kind of high pitched cross between a howl and a whine in the fat part of the torque band.
You could always just put a socket on the intake manifold bolts and the whatever else sucks air into the engine. You never know, some air might be getting by someplace.

 

[JoLin]

Re: 496 HO Whistling at 2000 to 2200 RPM (2002) - Cobalt 240

I lean toward intake noise too. And yes, it could be a dirty (or even bent) falme arrestor. Could even be the nature of the beast. There's nothing in a motor that 'whistles'. It's the harmonic vibration of air flowing into the intake that produces odd noises like that.

I had a 1980 Fiat Spider that I changed over to a free-flow air intake and filter. From that moment on I was known by other club members as 'the whistler.'

My .02

 

[Philster]

Re: 496 HO Whistling at 2000 to 2200 RPM (2002) - Cobalt 240

Normal.

Yes, it's the intake. Common on engines that use aggressive air intakes (often aftermarket intakes).

But on 496 HO... it is standard equipment.

For kicks, google: 496 HO whistle

 

[msojjo]

Re: 496 HO Whistling at 2000 to 2200 RPM (2002) - Cobalt 240

I have the same noise on my 350 mag. I was told it was normal, but it is still annoying. Its a noise thats hard to explain, but yes like a high pitched whistle or a whine.