1973 Rebuild

[SteveJ]

This is higher than the range for an E12-80, but that isn't a bad thing. https://pertronixbrands.com/products/pertronix-40011-flame-thrower-coil-40-000-volt-1-5-ohm-black?variant=31797269037092

If the tach doesn't want to play nice, you could go with the 3 ohm coil. https://pertronixbrands.com/products/pertronix-40511-flame-thrower-coil-40-000-volt-3-0-ohm-black?variant=31797269397540

[Matthew Abate]

Thanks! I’ll take a look.

The one I was leaning toward is the NGK 48776 which I’ve read is is rated at 0.93 ohms and falls in the range I mentioned.

If I understand correctly, more ohms is less heat, right? So the 1.5 or 3 ohm could you suggested would still be safe for the ignition.

—-

Also, I was reading through the ZHome write up on making a 240 tach work with a ZX dizzy and he calls out the 3-wire vs 4-wire tachs, 3-wire being his preference for making this work. I have a 4-wire tach, so I’ll have to dig more.

 

Edited August 4, 2022 by Matthew Abate

[Zed Head]

The 240Z tachs are the Smiths type current sensing tachs.  The instructions for the Crane ignition modules explain how to adjust the loop on the back of the tachometer to make them work correctly with ignition systems that pass more current.

Near the end of this document.  Pretty cool electronics nerd stuff!  Make it work.  -

 

[Matthew Abate]

@Zed Head I guess I didn’t really come out and ask, but I was more wondering if the ohms rating of the coil I choose impacts the tach wiring modification you’re recommending in any way, taking into account I have the 4-wire tach.

[SteveJ]

The current limiting was why I listed the 3 ohm coil as an option.

According to Ohm's Law in a DC circuit, V=IxR (voltage is equal to the current times the resistance).

Voltage will be relatively constant, so if you increase the impedance of the coil, it should decrease the current. The 3 ohm coil should give you about the same circuit impedance for the ZX distributor as the stock coil and ballast resistor with the points. Mind you, I have not tested this. I have a Pertronix 2 ignitor with a 1.5 ohm Pertronix Flamethrower coil in my 240Z. I jumpered out the ballast resistor, and my tachometer works fine.

[Matthew Abate]

Okay. Noted. I will include these details including the loop mod in the tach in my overall wiring plan. I’m not going to be able to test this stuff until I have it all in one place, unfortunately, but at least I have it all captured here for reference. Thanks guys!

Edited August 4, 2022 by Matthew Abate

[SteveJ]

I should also add that I had a Crane ignition in my 240Z for many years. I still had the ballast resistor in the circuit, and I never touched the tach or had any issues with it.

I suggest testing with a coil of 1 ohm or higher impedance first, then consider modifying the loop on the tach if there is an issue.

[Zed Head]

It really comes down to if you're trying to get the "most" out of the ignition system or not.  It's a matter of degree, and what you're trying to achieve.  The "high energy" (large plug gap) systems were designed to fire leaner fuel air mixtures I believe, with fewer misfires, for emissions purposes.  And to be more consistent over time, unlike points which can cause poor running as they wear.  

One side benefit of using a coil with more primary resistance is that the ignition module should see less current.  Which will generate less heat, which will make it last longer.  

When I installed a GM HEI module on my car I also used the GM HEI coil that it was matched to.  It was a 0.6 ohm primary coil.  Why try to out-engineer the engineers that designed it?  But I had the 280Z voltage triggered tach. 

SteveJ's plan is good.  Have options ready.

[siteunseen]

From what I remember the e12- 80 used 1.5 ojm coil from Nissan. That ps 20 is 1.4 so close enough for me. I had a bigger ZX cap and button and run ZX larger gap on my ngks.

It goes hard to Redline without breaking up. I have to up shift quick. Need a better gearing than the r-180 but I don't need to beat my car. It's 50 and has 50 year old parts back there. But those 1,ooo or so feet are fun and with my exhaust it screams a dry bloody murder like a Ferrari or a gsxr1. 

[Matthew Abate]

Time for a side quest:

In my continuing saga to clear my basement and get this Lego kit of a car together, I was cleaning the shift lever that came with it. Yes, it was a loose part in a cardboard box when I got it. Not, I didn’t get any info with it.

From what I can tell this is a five speed lever. The piece below the pin hole is 37.5 mm from the end of the ball to the crease where the lever becomes sort of spherical:

It’s identical to the long lever that came in my transmission, which is a five speed out of a truck.

I think I’m good to go, but if anyone sees a red flag here, let me know. This week has had a string of happy accidents, and the PO’s good up here worked out for me if my research is correct.

[siteunseen]

I put a 5 speed in my '72 but it popped out of gear. I removed the shift lever and saw some scratch and nick marks where it was hitting something, I can't remember what now but after I ground down where those nicks where it has worked fine. Just my experience, hopefully you will avoid this.

Here's some threads on the different shifters you can read through when you have time.

 

 

[Matthew Abate]

Yeah, these are the threads that informed my previous comments.

I’m glad you pointed that out, though, so I know the symptom to watch for.

I am pretty sure this is a five-speed lever and doesn’t need to be ground for a few reasons, not least of which because it matches the truck lever that came with the transmission.

Edited August 13, 2022 by Matthew Abate