MC2100, HEI, split header. This started very softly this morning, but got progressively worse.
I started getting a very high pitched whistle from around the carb itself. This was very slight only at idle, but within only a few minutes grew to a very loud scretching whistle at idle and under even load. If I put the engine under heavy load, the noise goes away.
It sounds like an air type whistle. I've checked the carb/gaskets for vacuum leaks with no luck. There is no loss of performance. I tore down the MC2100 and cleaned/blew out all passages and reassembled. No luck.
I started to second guess myself and began pulling belts off to try and eliminate a bad bearing in something. No change.
The noise is very high pitched. As I said, it goes away under load, but comes right back as soon as I lift off the accelerator. The pitch is fairly constant, but does seem to rise some when down shifting.
It seems to me that it has to be air either leaking out, or in somewhere... but I can't figure out where to look next.
Any ideas? It's so loud right now, no one wants to wheel around me... it's giving them (and me) headaches.