After you’ve acquired the basic components to convert your Z31 to turbocharged, there are still a few parts crucial to completing your conversion successfully. Nissan re-used a large number of components between both early and late model years and turbo / non turbo cars, but one component that had significant differences was the crankshaft pulley, seen here in the exploded FSM diagram:
The crankshaft pulley, also sometimes called the harmonic damper or harmonic balancer, is the pulley driving all 3 of the Z31’s accessory belts, as shown here in the FSM for turbo and NA:
The above diagram shows the main difference between the engine layout of the NA and turbo cars, with the alternator on the lower driver’s side of the engine on the NA cars, and on the lower passenger side for the turbo cars due to the turbocharger system occupying the driver’s side area of the engine bay. On 1984-1986 300ZXs, the NA cars used V belts for all 3 belts, while the 85-86 turbo cars used a micro-ribbed V belt for the alternator / water pump pulley. The pulleys and belts are otherwise exactly the same between NA and turbo, meaning swapping to the 84-86 crankshaft pulley will mean that you can purchase OEM style 300ZX turbo belts for maintenance, and that your belt system will be functionally identical to the OEM turbo cars.
As usual, the issue here is locating these crank pulleys. They are not common, with no examples on eBay as of the writing of this post for turbo 84-86 cars. Many for sale are damaged, with cracking or chipping on the edges that may result in vibration or stress on the crankshaft. I found a few in fair shape, but I decided I didn’t want to risk my engine’s health if I could find a better way. A few hours of searching and reading later, I came across a few old forum posts discussing CSPs and replacements, as well as aftermarket options. This site has information similar to the forum posts I saw:
“There are a few crank pulleys (harmonic balancers) available for the VG30E.
Unorthodox Racing (NLA)
Unorthodox Racing – 1.70 lbs?
Ross Performance – 10lbs .8oz
Stock (86 NA) – 6lbs 1.2oz
The Unorthodox pulley and Ross pulley have micro V for the alternator and water pump, while the A/C and power steering are V-belt.
The Unorthodox pully is solid aluminum while the Ross is carbon steel with a rubber dampener.
Ross Performance Nissan VG30 Z31 Metal Jacket Harmonic Damper
High carbon steel hub / pulley units
High carbon steel damping ring, fully bonded using an anti-vibration, anti-tear natural rubber
Damping weight optimized for much higher RPM and power level over an OEM unit
Aerospace grade anodized aluminium power steering pulley
OEM diameter water pump/alternator and A/C pulley to maintain optimal belt wrap
Under driven power steering pulley to protect power steering pump at high RPM*
Lightweight anodized aluminium timing disk
Laser etched 360° timing marks
Designed for use with our universal dry sump drive adaptor and 19T HTD pulley**
Steel components corrosion protected with a hot phosphate coating process and a high quality matte black paint finish
Uses grade 10.9 or better hardware
Complies with SFI spec 18.1
*power steering pulley is not underdriven
**a dry sump drive is not available for the vg30e
There is a lengthy wait time to acquire a Ross Harmonic balancer as each one is made to order. The overall quality and finish of the piece is immaculate. The fitment is perfect, the crank snout of the A/B series VG30E is 25mm, they machined it exactly and it slipped right onto the crank of my engine with no play in fitment and no fighting it.”
The Ross Performance Parts VG30ET harmonic damper is made in Australia, and comes with a glowing endorsement from multiple Z31 owners who have purchased it. It starts at $644 AUD, or about $450 USD before taxes and shipping. When they were available, new OEM Z31 harmonic balancers went for $300+, but as they are NLA for the most part the Ross harmonic balancer looks to be the best option available. I’ll continue to research Z31 CSPs for turbo conversions to see if I can locate any other manufacturers or high quality examples.