I switched from a 2G to a 3G alternator (160 amp) on my 351W and it seems that the belt isn't able to turn the heavier alternator fast enough and the belt squeals. At the same time I made that alternator change, I also replaced the stock fan with an electric fan.

Would this mean I need to adjust the belt or that I need a new one? I thought about adjusting my tensioner but wasn't sure which way - https://i.imgur.com/jUCDe.jpg

 

You could put an underdrive pulley on it and have more mechanical advantage.
With the serpentine setups most people just go to an 8 rib belt. (but that means changing all the pulleys)

I did find an idea in this thread. https://www.ford-trucks.com/forums/1...dea-tdr-p.html

 

Might want to pop the belt off and check the alternator real quick to make sure it IS a belt noise and not something internal to the alternator.

Mike

 

A little screech at startup is not uncommon when the 3G is retrofitted to V-belt applications.
Many of the serpentine guys swear by Goodyear Gatorback belts.

 

This isn't a little noise, it's a lot. And it doesn't seem to go away after sartup. Also, this is using the stock 6 groove belt, not a v-belt.

 

Yep, I know what you said.
Take the belt off and spin everything individually looking for any component that might be stiff or crunchy.

Perhaps the tensioner spring is getting weak after all these years?
A larger pulley will help the mechanical advantage without affecting output much except at idle.
The guys that really use high output 3G's for winches and the like, usually go to an 8 rib belt.

 

I took off the belt last night and spun each accessory, all spin freely. The alternator pulley is really hot due to the friction so it has got to be coming from there. I wouldn't mind going to the 8 rib setup, maybe down the road. How do I measure my current pulley to know what size larger one to get? Do I need to measure the circumference or the diameter? That seems like a good solution for now. I also wonder if I need to buy the 8 rib pulleys individually or if there is a kit.

Thanks.

 

Diameter.

IIRC there's 2 1/2, 3, 3 1/2" etc...

Eight rib setups are a PITA to implement, but since you already have a supercharger, Vortech and the like all sell 8 rib kits.

 

Are you sure the squeel is from the alternator? I replaced my alternator a couple months ago and the tensioner went bizerk! swapped it out in about 5 minutes and no more squeel.

 

Other then crank pulley, 8rib pulleys are easy to find. They are on all powerstrokes and sc lightning and sc cobra and 99+ f450-550 or even tbird supercoupe

Then Paxton or vortec sell 8rib for mustang apps so maybe it will lign up with truck acessories.

Larger diam pulley is what's needed. Not enough belt wrap for the draw. I put a "100amp" replacement on my truck and all it was I think was my 85a with a smaller pulley. I'm happy only cause it charges better at idle, but I was hoping I didn't need to go with a 3G. New rebuilt on eBay only cost 40 shipped and no core. I'm not concerned. I'll keep my eyes open for a cheap 3G. May score a new one at jy in a few weekends.

 

Your photo tells me the belt you have is too long. That tensioner should have a lot more preload on it. It's almost at the end of it's travel length. There is no belt tensioner adjustment, it's spring loaded.

 

You're right!
That tensioner is way out of range.



I don't even bother to follow links in posts if they aren't referencing another thread.
It only takes a second to insert a photo and make things clear.

 

20 lashes with a wet noodle

 

So far, so good. But I only had the truck running for ~30 seconds or so - I'll play around more this weekend. When I started the truck, the new belt squeaked a little but eventually things caught up and at a steady 1000 RPM (cold idle) I was getting 14.2 volts, 1 volt more than last time with the older belt.

Thanks!