But what does the tachometer needle do?  Usually there are other things that happen that can give a clue about the main problem.

Here's a link to the HEI module conversion - http://www.zdriver.com/forums/240z-280zxt-s30-s130-tech-tips-275/turbo-ignitor-swap-upgrade-chevy-hei-27569/

 

You might also check the power transistor wires and the ground circuit of the mounting bracket.  It's very exposed and the wires aren't very durable.  Plus I think that the transistor grounds through the bracket, so a dirty or loose bracket can affect its operation.  The whole thing looks cobbled together, like it's from Radio Shack.  Check it, clean it, tighten things up, and use a meter to verify grounds.

I only had a comment  on the issue of the head bolts.  Always use new ones. As was so completely stated they are one use bolts.  I do recommend using copper coat on the head gasket and  IMPORTANTLY  use ARP torquing grease on  the bolts .  It makes a big difference.

Tach needle behaves itself - no dropping to zero or anything like that. 

the head bolt issue was resolved in 2014, but as noted above, I'm still working to get the car right.

Three years later: What I finally did after messing around with this missing and bad running problem for more than a year was to find a Z mechanic in town. I knew an import shop that had some experiences guys, and I called and found out that one of them had been a Z-car mechanic in a Datsun dealership years ago.

I took them the car, explained and demonstrated the rough running problem, and also an oil leak on the timing gear cover which I was forced to remove and re-install after the head was on.

My request to them: make it run right. Keep it as long as you need, I'm in no hurry. I also asked them to replace the steering rack (the seals popped when I took it off the jackstands it had been sitting on for nearly four years)  and install some poly bushings I had.  In other words, I was really tired of messing with it. I've done a steering rack on a ZX and I just didn't feel like repeating that exercise at age 67.  

Got it back four months later, and $5000 later. I wrote that check with a clear conscience, because with it running right I have at least a $9,000 car. Without it, I had a $2000 body with a problem engine. The $5K was worth it! (Especially with a new steering rack and a set of good poly bushings all around.)

The problem was mostly vacuum leaks. The 83 ZX turbo has a nightmare of vacuum lines and they had the equipment to check them all and the experience to see what the problems were.

I'ave had Z-cars since 1974 and this was my 4th one, but this problem was beyond me. 

Congrats on getting it running. Hope you are still having pleasure driving it.

It's very nice to drive! The biggest thing I notice is the noise level when I get to highway speeds. I installed a radio with Bluetooth connection, but at 70 MPH there is enough overall wind and mechanical noise that I can't hear callers and I don't believe they can make out my voice above the noise level.  That's with door and window seals that are only about 6 years old. Driving a 30+ year old car is a fast reminder of how mechanical they are and how much difference there is with my 10-year-old BMW 3-series (six speed manual.)

But I didn't buy it to have conversations, I bought it to have fun driving it. So, no problem. In town it's fine.