Whistleing or squealing noise at 700 to 1000 rpms

[km74]

Hello I just purchased a 51 170A. It is in beautiful shape and flys great. It cruises at 120mph IAS at 2400 rpm. It has a whistleing or squealing noise(I can't tell exactly) at 700 to 1000 rpms that goes away if you are above or below those rpms. It has 2 venturis and it sounds like the sound might be coming from around that area. Has anyone had anything like this happen with their airplane. It has done this from day one and I have put 15 hrs on it with no change better or worse. Any comments would be appreciated. I cannot go out and start it up now because I am working for the next week. Thanks for any input

Ken

[Tom Downey]

It has a whistleing or squealing noise(I can't tell exactly) at 700 to 1000 rpms that goes away if you are above or below those rpms. It has 2 venturis and it sounds like the sound might be coming from around that area
Ken

MY 170 did it too until I removed the venturis. Early 172s did it also.

[km74]

Thanks for the info Tom. I sent a friend out to the airport after I posted this and got him to put socks over the venturis and sure enough it didn't do it. I guess I will just have to get used to the sound. I found it odd because my 120 had a venturi on it but never made a sound. This one has 2 on it on the left side, so maybe that is what makes the difference. Thanks again for the reply.

Ken

[doug8082a]

I have a '52 with a single venturi on the right side... it does the same thing. It's annoying, but I've gotten used to it. When my passengers get bored waiting to takeoff on a hot summer day, they hang an arm out the window, pat the end of the venturi and play a tune

Doug.

[GAHorn]

It's not nearly as annoying a sound as that ripping noise a personal check makes when you tear it out of the checkbook to pay for yet another vacuum pump!