What Did You Do To Your Chevelle Today

[earthquake68]

Originally Posted by fleming23

Been trying to tune my new 4L80 for WOT shifts but I keep throwing the stupid alternator belt, or flipping it, nearly every time I get on it hard. Also difficult to do on any roads around here and half expect the local police to be waiting for me at the front of the neighborhood every time I come home... I picked up a late 80s 454 crank pulley with a wide 5 rib alt. belt but could never find the water pump pulley I wanted/need. Anyway, decided to order a Black Mountain Precision 1" cog belt system this evening. From everything I read, this should help with my alternator belt issues.

Now just need to identify why I have what seems like a motor miss at 5k in 1st gear when accelerating at WOT.

Ready to get back to the track and run this thing!

I had the same problem with my first Chevelle. It turns out the alternator pulley was worn out. The belt is supposed to be suspended above the bottom of the groove in the pulley and ride on the tapered part. When the pulley wears out, the belt will fall to the bottom of the groove. It won't matter how much you tighten it, it will slip. I'll bet money if you replace the belt and alternator pulley, you won't have that issue anymore.

As far as the miss goes, check the seat pressure on your valve springs. You may have a bad spring floating when you get up in rpm's. It could also be a pick up coil or ignition module. ...Just some things to check.

[fleming23]

Originally Posted by earthquake68

I had the same problem with my first Chevelle. It turns out the alternator pulley was worn out. The belt is supposed to be suspended above the bottom of the groove in the pulley and ride on the tapered part. When the pulley wears out, the belt will fall to the bottom of the groove. It won't matter how much you tighten it, it will slip. I'll bet money if you replace the belt and alternator pulley, you won't have that issue anymore.

As far as the miss goes, check the seat pressure on your valve springs. You may have a bad spring floating when you get up in rpm's. It could also be a pick up coil or ignition module. ...Just some things to check.

Thanks!

The Alt. pulley is nearly new, as are the rest of the pulleys. Actually put on a much larger alternator pulley with a deeper groove to try and slow the belt down a little but it is still flying off.

I think I have a solution to the problem on the way though.

What I don't understand about the miss at 5k is that after about .5 seconds the car picks up and pulls all the way to 6200 or so where it shifts. I did replace the module with another I had sitting around and will swap out the coil with a D.U.I. 50k coil later this week just to eliminate those from the equation. I found a few threads with similar issues related to the MSD Pro-Billet HEI distributors and it was often suggested that the modules are not the best. I'll see.... Hopefully nothing too difficult to pin-point.