I have finally finished getting the car back together. For the most part everything seems ok, but I have 2 new issues.

For reference I did the following modifications while I had the engine apart: 6% upper pulley, 4.2L crank pulley, gen 5 SC, bored throttle body with new butterfly.

The 4.2L crank pulley has been done by a few members here. You need to run a 6 rib belt rather than the stock 7 rib for the accessories as the 4.2 pulley is 6 rib. I used a K060935 belt as suggested by Avos in an older the thread. The belt appears to fit very well. However when I start the car this happens:


The belt moves from side to side on one of the idler pulleys and skips on the alternator like crazy. I also have a mysterious battery not charging message that has come out of nowhere along with a battery light on the dash.

I removed the belt and inspected all of the pulleys. They all seem completely fine. None of them wobble etc. while the engine is running. The alternator pulley also turns over with no issues either. I'm not sure if the message is real or not as I let a friend borrow my multimeter.

Did any of you guys running the 4.2 pulley have this issue?

 

Odd, i have none of that. did you ensure that the belt is set on the same six ribs of all the pullies when you installed (i.e. the front 6 vs the back six.) I dont recall now which I did.

 

When placed on a surface plate the inner 6 ribs (toward engine) on the original pulley line up with the 6 ribs on the 4.2 pulley. So the belt must ride on the inner 6 ribs on all of the remaining pullies. That is how I have it set up every time I go to start it. I think the issue is the alternator. It does not appear to be functioning if the car is correct. I will confirm tonight with a multimeter.

My theory is if the alternator is failing it could be putting up enough resistance where the belt is getting backed up as it rolls over causing enough slack for the belt to move around on the idler. If that's not it then I have no idea. I have an alternator on my parts car I can try.

 

The alternator is only putting out around 12.5 volts at idle. That seems too low. I'm going to swap it out for the one in my parts car and see what happens.

 

That is where the belt is walking, it's moving between ribs on the alternator pulley hence the movement onto the tensioner pulley. I would be adjusting the alternator so the belt comes off it straight, or it's likely to damage the bearing - it looks like it only needs a little tweak.

 

So it turns out the alternator was definitely bad. It put up much more resistance than the one from the parts car. If I spun it it would not make a single rotation before stopping.

I got the car back together and started it up. No more loud whine, battery light, or battery warning which was great! The belt still skipped.

To plan ahead I bought another belt incase the first one got damaged. That belt is a gates HD, whereas the first one was a CRP. By chance the gates has much deeper grooves, and after swapping it into the car the noise stopped!

That was great, but the belt still doesn't look totally happy. I guess I shouldn't be surprised, seems I was a little overly optimistic. I agree that it probably needs a slight adjustment. I'll get some shim stock and see what I can do. Very happy for now though.

 

If the belt had been skipping a while and the alternator was as stiff you say, then I'd give the pulleys etc a good eyeballing. I've seen our style of belts melt slightly into the grooves when slipping & then that lump of rubber in there makes the new belt jump about. When I had it years ago, a good wire brush cleaned the pulley out fine.

 

When modern belts skipps it metlts and therefore looses it's grip. Many cases belt gives rubber coating to the pulley grooves so that new belt wil not grip until grooves are cleaned good.