It's a 2.6 block and head, 2.3 stuff bolted on all around. Including the timing belt.

So I opened it up to set the valves and also stick in a delta cam I just got, so I took off the timing belt upper cover. What I notice is, the belt is hanging off the sprocket by 1/8 inch. That leaves about 3/8 inch of the width of the sprocket showing bare. In other words, the belt has slid sideways (forward) about 1/4 inch from being centered. the belt shows signs of rubbing...the edge is showing metal fibers like the steel in a radial tire...at least it looks like metal. when I turn the engine over with a remote starter, I can see that the belt rubs against the inside of the lower timing belt cover.

Shining a flashlight down into the lower cover, I see that on the next sprocket down there (oil pump) the belt is equally off center. And the tension pulley too--that is, the clean spot where the belt has been running begins at the center line and runs forward.

I need this to run, so my plan is to set the valves, cover it up and run it until next weekend. I will plan on pulling radiator, belts, pulleys, etc, and having a new belt in hand.

But meanwhile...any ideas what is causing this?

P.S. It is an 86 P'up, everything stock (carb,etc) except I replaced the 2.3 block and head with a 2.6 rebuild (guaranteed for 40000 more miles).