Throwing PS/Water Pump belt on 340

Just went through this myself, tossed a belt at 7,000 rpm going down the track. One of those things you don't think about until it happens then you find out it's a common problem.

Did some research and found a shim kit for the WP and crank pulleys. After the shims were installed, the alternator was at a slightly different depth and angle than the other pulleys. I had to put washers behind the alt. brackets and in front of the spacer behind the top mounting ear to get it lined up and angled right. Have not spun it up too high yet but visually it looks better than before the shims.

I was running a repro pulley set and the WP pulley was not machined correctly making the belt ride up a little higher and twist slightly in the groove. You could see it from the side, one side was much thicker than the other. I replaced it with an old OE pulley which had a more evenly machined groove, the belt sits much flatter now. Fingers crossed.

Also, if you look closely with the car running you can see the accessory brackets flex when you whack the throttle and the motor torques over. It's easy to see how you toss a belt, especially if you are on and off the throttle causing the belt to slack for a moment then spinning it back up high again.

And FWIW, a lot of people recommend a Dayco top cog belt. I had a Car Quest/Gates belt and switched to the Dayco when I replaced it.

Going to start carrying extra belts with me though, just in case.