Today, I was driving my 66 mustang home from work, and I noticed this screeching sound when accelerating. The car performed normal, so ya, it has to be the belt right?

But when I let it warm up there wasn't any screeching at all, only when i drove it, and it only happens sometimes, which I find really strange.

I got home and put it in park and revved it a little and it started making the noise again, then it went away. I turned off the car, and looked at the belt on my March pulley setup (it is a basic setup, had it for like 2 years, with just a Carquest belt on it). The belt seems like it is in good shape, what could my problem be? I am going to take a better look at it tomorrow when it is sunny outside though. Thanks.

 

its the belt starting to slip replace it you will most likely see some glasing on the sides where it rides in the pulleys.

 

A belt should be tight and to check, push down and pull up - it should move no more than a half inch. And as mustanglover66 stated, if the belt is glazed or the groves on any pulleys have a blackish look to them, it's new belt time.
Jim

 

I'm also going to vote that it's the belt squeaking. However, I've usually witnessed a problem belt squeak less as it "warms" up (friction, bending, etc). This seems to be the opposite for you, as it gets worse as you continue to drive. Unless you meant "only when you accelerate past an idle", in which case that makes sense.

One last thing, I've had some moderate luck with the "belt spray" that they sell at the local auto parts store. Don't expect miracles, but if you're glazing is minimal it'll give you some traction. You're experience with "snake oil" remedies may vary!

Good luck.

 

Check the water pump pulley too. Sometimes if the bearings are going then there is some play in the pulley.

 

I gave it another look, and I did notice like you guys said, kind of a burnt rubber on the edges of the pulley, so I will just have to get my hands on a new belt and it will be good to go. Maybe I'll tinker around with it a bit today and just take it for a spin just to reassure myself I guess.

 

As mentioned, check for glazing on the "traction" side of your serpintine belt. Once they slip a little, they are history,,,,,

 

Serpintine belt - on a 66 Mustang? Difficult to picture on a 289.
Jim

 

I jumped the gun a little, I saw that the poster had installed a March pulley setup, so I assumed serpintine,,,

 

just get a new belt and make sure you have the proper tension on it, it makes that noise cuz its too tight or too loose