I can't figure out for the life of me why the belt keeps sliding off one rib. Everything looks aligned, and installed according to spec. I'm baffled... Anyone have any ideas?

 

Only one thing can cause that. Pulleys are not perfectly aligned. Double check your installation and if necessary call the front end accessory vendor for clues to look for to check alignment.

 

Do you have the part number?


What engine are you running? What accessories?


Can you get pictures of each accessory and its mounting points?

 

My burb started doing that after I changed out the water pump. Of course I had to reuse the smooth pulley from the old water pump but the shaft on the new pump must have been a tad shorter and the smooth pulley had a slight groove worn into it. The problem went away when I ground the lip off the edges of the groove to make the pulley smooth again. I did it on a lathe with a file but I imagine a sanding disk on a grinder and a little care would be good enough.

 

351w, March pulley kit, water pump pulley is smooth now

 

That is one nice looking engine. Don't look at it without eye protection in direct sunlight!

 

I would look into the alternator. Make sure the housing isn't too wide (pushing the alternator further out) Do all of the other pulleys line up except the crank? I cant imagine them requiring a spacer for the crank pulley to the balancer. Do they recommend a specific harmonic balancer?

 

Doesn't seem like all the pulleys should have ribs; are all the idlers/tensioners installed? I can't see a belt path that works for that. I'd expect the WP pulley to be smooth.

 

I wonder if you have the wrong balancer. There are two lengths used:
3.875"
3.950"
The 3.950" is the most commonly used ones for the 302/351W.

 

He says he has a smooth pulley on the water pump now, I'm wondering if the pulley is fully set on the steering pump.

 

I ran into a similar problem when I installed the V/A frontrunner system on my 351W. The aftermarket harmonic balancer did not stick out as far as the OEM version so I had to buy a spacer to correct the alignment. Much to my surprise I found a vendor online who sold such a spacer...turned from billet and included the proper mounting bolts. $23 later I was on my way. You can see the spacer in the photo, it sits right behind the crank pulley.
The power steering pump pulley was also a little tricky to get in alignment...no adjustment other than how far you press the pulley down on the pump.