I have been after a serpentine UDP set for a long time now. I am just collecting and bastardizing some from other vehicles for completion.

You might have to do the same if you cant find what you need.

I reckon the bigger pulley may weigh less -- it doesn't use the cast metal spacer that the smaller pulley does

Its on my race coupe i do not want to put any bigger pulleys on more weight.

A couple of guys were asking about them, but I don't recall anyone making them. JTS supposedly had them at one point

Instead of underdrive crank pulley you can fit overdrive water pump pulley. If your fan has the 103 or 107 mm pulley, swap it for the 129 mm pulley. See Water pump - section "Pulleys"

Would anyone recall which member was making small crankshaft pulleys for A series motors was years ago.???

Nismo used to sell underdrive pulleys (smaller diameter than stock pulley)

* 99996-H1160 SMALL DIAMETER CRANK PULLEY -- has a diameter of 101mm, works with stock accessories (compare to stock pulley at 139mm or 129mm)

* 12302-H5720 SMALL DIAMETER CRANK PULLEY -- diameter of 75mm, requires special belt and accessory pulleys

Yes, smaller crank pulley is said to prevent water pump cavitation which is reportedly a problem above 8000 RPM. But it won't help overcharging, if anything will cause undercharging until substantially above idle (the Voltage Regulator controls overcharging)

Datsun water pumps were cast iron impellers by Atsugi or Hitachi, and are supposedly less susceptible to cavitation

Newer Nissan and aftermarket pumps use pressed steel impellers, much cheaper to make, and are reportedly more likely to cavitate

Its a smaller pulley that slows down the other rotating pulleys. Stops water pump cavitating and alternator over charging at constant high revs.

Pm sent

What's an underdrive crank pulley?

I am looking for a underdrive crank pulley to suit A14 engine.
Any imfo would be great.Greg.