I have a 1966 mustang with the 289, I’ve been having a problem recently where once the engine reaches normal operating temperature, a high pitched whistle sound like a tea kettle steeping begins and doesn’t stop until the engine shuts off.

The sound is consistent regardless of rpm or speed and is so loud it’s hard to tell where it’s coming from.

I have changed all the vacuum lines and the pcv valve and have been through 3 Holley dual barrel carburetors with no change. I bought a smoke tested on Amazon and tried to test the engine but no matter what like I placed it in or shoving it down the carb there were no visible leaks from any line nor the brake booster. I’ve tested all the belts as well and none of them nor their pulleys are making the sound.

any advice?

 

Just finished changing the intake manifold gasket which was a bit burnt but when I replaced it and re torqued the manifold it still makes the sound. Here’s a link showing the noise. ​https://youtube.com/shorts/Z4xRjaGUFVU?si=3BIa1bCzU0DKgtqw​​​

 

The link to your YouTube video is connected to your statement, I tried separating the two, but it still won't open.

 

Copy/paste just the 'http' address to a new tab, and open it,...it'll work.
I've heard of using starter fluid to find intake leaks,...if sprayed near enough to a vacuum leak, with engine at idle, the engine rpm will rise - I believe that is correct. Most common intake leak (other than carb gasket) is intake manifold gasket.
Best of luck with your car!

 

I had the same problem a few days with my 1966 289. I´ll switch to spanish that is my native language. Hope you can understand it, or traduce it with some app.
Encontré que la manguera de vacío (part # C6AZ-6A664-N) que va desde el carburador a la tapa de válvulas colapsaba por la fuerza del vacío que genera el carburador, generando un silbido bastante fuerte y molesto. Dado que no tenía un proveedor de repuestos cerca, hice un espiral de alambre que introduje dentro de la manguera, evitando así que colapsara con la fuerza del vacío. Ni solución funcionó muy bien.
I don't know if your problem is the same I had, but I hope this can help you.
All the best.
ChrisVilla

 

Here's the translation for you, ChrisVilla:
"I found that the vacuum hose (part # C6AZ-6A664-N) that runs from the carburetor to the valve cover would collapse under the force of the vacuum generated by the carburetor, generating a rather loud and annoying whistling noise. Since I didn't have a parts supplier nearby, I made a wire coil that I inserted inside the hose, thus preventing it from collapsing under the force of the vacuum. Neither solution worked very well."
That would require a stiffer vacuum hose, to solve the problem. Just as a thought,...a large spring might hold that hose open, though,...