Alan 91 C2

The low charge voltage at idle, was frustrating. So I upgraded my V Belt with the help of a later 87 rib belt pulley. As some may know, the V Belt alt pulley, was in 78-81 cars. 82 -83 4 rib belt. 85-86 5 Rib. 87 6 Rib.

Basically machined alt drive V belt pulley, and welded 87 6 rib pulley. Good voltage at idle using small diameter 6 rib alt pulley. The belt spacing is close but workable.

Rob Edwards

What's the diameter of the later multirib alternator pulley at the crank? An early alternator crank pulley is 130 mm OD, an early alternator pulley is 63 mm. Since an S4+ alternator pulley is roughly 50 mm (measured on the ribs), if the S4+ crank pulley is roughly 130 mm you're getting 25% more alternator rpm at idle- a nice bump.