280zx Alternator shaft diameter

[AK260]

Hello gang!
 
Been about 2 years since I properly saw the Z and played with it. But being on gardening leave, I’ve finally got time again.
 
I’m using an ATi super racing damper, which has a 70mm pulley - to reduce parasitic losses. Yay for free BHP and boo for alternator spinning at just less than half speed, not producing charge at idle revs! Most alternators do nothing of note below 1200-1400 shaft RPMs.
 
To combat this, I had it professionally rewound to produce earlier + modified a 63mm pulley on a lathe. This reduced the issue but the voltage needle still dances at idle until about 1300rpm which I don’t like, especially as the lights dim then go bright with rising revs.
 
So, I’m about to fashion 2 other pulleys to experiment with - one with a 50mm OD and one with 40mm.
 

 
 
To do this I need to drill out the centre of a blank pulley - for the life of me I can’t recall the size. 17mm seems to ring a bell and a nut I “think” I bought for the alternator but never used seems to confirm it. Or is it 18mm to account for the thread depth?

But I thought I would ask here as someone may know and save me taking the alternator off the car and removing the pulley to measure.
 


So come on! Fess up! Who else is man enough to publicly claim they have a 17mm shaft!?

[Zed Head]

Might find it in a bearing cross-reference somewhere.

https://www.carpartsmanual.com/datsun/Z-1969-1978/electrical/alternator/12v-60a

https://www.nissanpartsdeal.com/parts/nissan-bearing-ball~23120-65004.html

This popped up on the Google.  Read the description closely.  17 seems right.  Has the Nissan number shown.

https://smithcoelectric.com/products/5-4700-new-bearing-17mm-x-47mm-x-14mm-17x47x14

[AK260]

Thanks buddy, that’s great.

[AK260]

Well it was most definitely 17mm.

So I got the smallest pulley I could realistically get onto our alternators (47mm OD 40mm PCD) and bored it out to make it fit.

I took a little too much material out of my first attempt - broke as soon as I tried to flex it! ;)




It’s sorted out my discharging at idle issues and the voltage is a lot more stable. With the ATi damper and pulley (70mm) I now get a 1:1.5 ratio meaning my alternator is actually generating at an idle of 1k rpm. Now to find a new belt as it’s right on the limit of the adjuster.