I'm putting a large case 1G 110 amp alternator on in place of the original small case 60 amp unit. Truck is a 460 with factory air. Engine is modded a little and the trans shifts at 5600 rpm at WOT. I'm concerned about the 1G spinning too fast with the stock pulleys and throwing the windings... The alt has a 2 1/2" pulley. I think with the existing crank pulley it will be turning about 17,000 RPM when the trans shifts. Anyone know the max RPM on a large case 1G?

 

Doing a Googley search for "maximum rpm ford 1g alternator".. the max RPM is like 18,000 rpm.

 

Yeah I did that but I think the 18K RPM is for the small case 1G...the rotor/stator is a lot bigger in diameter on the large case 1G.