What is the specified idle RPM for the Mark VIII?

In drive it should be an exact and steady 600 rpm's.

In drive it should be an exact and steady 600 rpm's.

Thanks. For some reason, I could not find the spec in any manual I have?

Anyways, I measured the crank pulley at 6-3/4" diameter and the alternator pulley at 2-1/2" diameter for a 2.7:1 ratio. So, 2.7 times 600 equals 1620 RPM for the idle speed of the alternator. Most alternators publish their idle numbers at 2000 RPM it seems. And most idle numbers are half the rated amperage of a high output alternator(i.e. 160 amp alternator gives 80 amps at 'idle').

I measured the output of my alternator at 20-25 amps at idle. I'm looking for a high output alternator that will give me 55 amps plus at idle. If the output was linear(which I know it is not), I would need one that gives 70 amps plus at the manufacturers' idle of 2000 RPM. So it looks like I'm needing a 140 amp plus... so I'm thinking 160-170 amps.

Next question... what is the diameter of a typical underdrive crank pulley?