"Howling" noise

Pulse air injection system. 328 is famous for it and the noise is not made by all cars and only happens in certain narrow temp and climate conditions. Pulse air shuts of over a certain RPM or throttle position, don't recall which. Also goes off when coolant temp starts to rise. It draws its air from the right fender vent and generally is loudest on right side in and around the air induction plumbing. Sounds mechanical but is a result air pulsation of the reed valves.
You have described it pretty perfectly. It has a temperature below which it does not operate. It has a temperature above which it does not operate. It has an RPM or throttle position above which it does not operate.



https://algarferrari.com/store/parts/6-8-cylinder/328-group/328-gtb-gts/table-10

 

This has been VERY informative. A very limited search online seems to show that in some cases reed values could be tested / replaced on some cars.
Does replacing anything improve this or is it just something that happens and you live with it...? Can it be "fixed."

Sometimes the diaphragm in the regulator of my gas grill hums, but it just is what it is.... Part of life.. Is that what we have here?

RifleD: You are a true gift...

 

A/C Compressor belt or bearings ?

 

On rare occasions my '87 will make the noise but a blip of the throttle ends it. And, indeed, it only happens in cooler weather. I've owned the vehicle for nearly 34 years and have never used synthetic oil in it.

 

Next time you hear it after starting, jump out, open the engine cover, and place your hands on the check valves. You might be able to feel it.

 

Great Thread!
My 87 - 328 makes the same noise during cold weather - cold starts(Dallas, TX). Once the oil temp gage moves (oil warms a little) the sound stops. This usually is 2-3 minutes engine running and a 10th of a mile drive distance. I just live with. Glad to hear it's nothing major.
Cheers Mike996!

 

I forgot to mention... I have a Tubi exhaust. I thought it it had to be warmed up a little before the whistling stopped. LOL
Temp greater than 75 degrees, no whistle.