Just put a new engine in my '92 Bronco 351W. I crawled under it today to do it's 500 mile break-in oil change and noticed that the serpentine belt is shredding itself on the front edge.
At first glance it looks like the crank pulley is the culprit since the belt is riding on the front lip while it's seating correctly in the other pulleys. It's also riding too far forward on the water pump pulley, but that one's flat and runs on the back of the belt so it's not damaging anything. I ran a straightedge across the crank and smog pump pulley faces and they seem to be OK. I tried it with the power steering pulley and it seems to be a little too far forward, but the belt is seated in that pulley just fine. Besides, I don't know if the pulleys were set up by Ford to be referenced against each other off the front edges.

My question is this- is it possible for the harmonic balancer to be installed too far back? I rebuilt the original engine with the same crank, balancer, timing cover and all the other external parts, and it didn't have any belt problems before the engine came out. I thought the balancer seated against the front main so it couldn't go too far back. I could put shims between the pulley and balancer to correct the alignment, but that seems kinda Mickey Mouse and I've never heard of anybody having to do that. Or is the belt getting forced forward by one of the other pulleys and hitting the lip on the crank pulley because it's the biggest diameter and the one getting all the torque?
This thing is really wigging me out. Any input would be appreciated.

Oops, just realized something. I replaced the timing set with an Edelbrock street legal true roller, so I wonder if the crank gear is thinner than OE. It would have to be at least 1/8" thinner to cause this problem. Anybody else have a timing gear issue?

 

The balancer should seat on the crank nose - it's not likely it failed to seat. Check the P/S pulley to make sure the silver pump shaft is flush or slightly proud of the P/S pulley. I had a P/S pulley begin to slip off, and the first symptom was one shredded groove on the belt. If the pump shaft is recessed into the center of the pulley, there's your problem. If you get a 3/8" bolt (not sure if it's fine or coarse) and a large washer, the bolt will thread into the void in the pump shaft (the silver thingy in the middle) and pull the pulley back onto the shaft. The pump shaft has a boss on it, so the pulley will be located correctly when you pull it back on. Just like using the cleaning your ears with a Q-tip, stop when you meet resistance!! Of all the belt driven accessories, this is the only one not secured by a bolt/nut/and lockwasher. Let me know if that fixes it!
Good luck,
Cheggie

 

Ford has a lot of bullitens out on overpressing and underpreesing ps pulley to correct belt misalignment and belt noise concerns.

 

The P/S shaft is flush with the P/S pulley, just like it's supposed to be. I went back out last night and stared at it for a while. I finally took the P/S bracket off and removed the timing cover stud that the lower left corner of the bracket sits on. I put the bracket back on without the stud and it seemed to correct about 90% of the misalignment. I must have put the wrong stud back in that hole in the timing cover during the rebuild, even though I took notes of the stud/bolt arrangement. The hex part of the stud is about .060" too thick, and it kept the P/S bracket from seating all the way, but I couldn't tell by looking at it from the front due to the A/C and the other crap being in the way.
I managed to rig up a bolt/washer arrangement that lets the bracket seat properly and still seals the timing cover and water pump. It ain't perfect, but it's a lot better than it was. The real test will be to see how long the new belt lasts.
I was underneath it watching the crank pulley spin and I noticed something else- the harmonic balancer looks like it has quite a bit of runout. I didn't have time to put a dial indicator on it, but it was easy to see it by eyesight. Great.

I knew this rebuild went too smoothly. No leaks, no smoke, runs like a clock. I was expecting bugs, so hopefully this is it.