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1973 Rebuild


Matthew Abate

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Okay, cool! Thank you. I passed this info along and we will see where it lands.

In other news, I have the dash harness out and have been investigating the condition of the dash and all of the components. One thing I want to do is figure out the tach + ignition combination I want to go with. I am trying to make this electrical system as clean as possible from the get go, so if I can figure this out now it will be better.

I am 90% sure I am going to go with an E12-80 ignition on a 280zx distributor. My engine is a ZX block and head, and even though it’s set up like a 1972 with SUs, that ignition feels right.

So that means tach problems, since mine is a ‘73 tach. I watch a video on swapping a ZX tach instrument into a 240z tach housing, but upon further investigation I think the guy misspoke and actually used a 280z tach instrument in his mod.

I know there can be issues with a 280z tach and an E12-80 ignition, so I want to look into this further. I see a clean 280z tach online that is complete, but I also see a few 280zx instruments that are in my budget.

@SteveJ @Patcon @Captain Obvious, Based on your comments on other threads related to this I thought maybe you guys might know if the ZX instrument has the same bolt pattern and dimensions that the 280z and 240z instruments have. If so, this really simplifies my approach.

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I'm not sure what issues you are referring to. I'm pretty sure the 240Z tach will work with a 1.5 or 3 ohm coil. There are no issues that I'm aware of with a 280Z tach and matchbox. A previous owner swapped out the distributor in my 260Z for a matchbox, and the tach works fine. I've helped a friend with the conversion, too, on a 260Z. That tach is the same as a 280Z tach for all intents and purposes.

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Page 16 here might help if you run in to problems.  The Crane systems are electronic, like the ZX modules, and, apparently, people occasionally have problems when they convert from points to electronic.  They describe how to adjust the tach.  It's the system that the 240Z uses.  Pretty sure that others have mentioned the same adjustment in past threads on the forum.  It's not obvious.

https://static.summitracing.com/global/images/instructions/xr700 instructions.pdf

I also uploaded these to the Downloads area - 

 

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There sure are a lot of ifs in that write up. Given the state of disassembly of my car I’m wondering if there’s a way to eliminate some of them in advance.

But if I’m understanding @Zed Head correctly I may be able to use my 240z tach with a 280zx distributor, which will same me a pile of cash, for sure. Would be nice to wire this up correctly so it’s nice and clean and doesn’t need to be opened up later.

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Posted (edited)

Back to the tach… I’m getting ready to choose a coil to go with the e12-80 ignition on the rebuilt distributor I just bought. @Zed Head posted an image from an 81 FSW that says the correct coil resistance is 0.84 - 1.02 ohms in another thread on coils for this ignition.

I guess what I’m wondering is if this will impact what we were talking about with the 240z tach continuing to work with this ignition/coil combination, or if maybe it might present an issue. I don’t fully understand this stuff.

I’m going to get a coil in this range either way because I want to match it to this ignition, it just impact other stuff down the road.

Edited by Matthew Abate
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Posted (edited)

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 by Matthew Abate
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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.  -

 

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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.

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Posted (edited)

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 by Matthew Abate
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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.

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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.

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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. :beer:

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  • 2 weeks later...

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:

76CC922A-F6EF-443D-A1DB-F7CEE629A031.jpeg

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.

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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.

 

 

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Posted (edited)

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 by Matthew Abate
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Posted (edited)

I have a couple of updates:

1. The first half of the dash harness inventory is up in my wiring build thread.

45B880E0-5364-4735-BA68-4A8A317CCFC5.jpeg

Now that that’s in the bag I’m moving on to the second half of the dash harness.

A9FC0BA6-ABCD-4DD4-B68C-BC6A9E75E0EF.jpeg

 

2. I’ve been trying to sneak in small things to help me feel like I’m making progress. This week’s small thing was the head liner.

3BB2B551-39B6-45D0-AE31-0A73835A7104.jpeg

3D11AAF6-88D0-4623-AB99-8751216942AD.jpeg

IMG_4916.MOV

IMG_4934.MOV

 

Nice and quiet!

Edited by Matthew Abate
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Posted (edited)

Oh, I should add that I tried just having strips of dynamat, but it showed through the headliner. If you’re going to use any you have to cover the entire roof, and you have to get it on as smooth as possible. The headliner is surprisingly bad at hiding bumps and ridges under it, despite the thick foam backing.

Edited by Matthew Abate
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Posted (edited)

Some updates:

1552989F-70DA-4C2E-AF0C-D6CF12316C52.jpeg

Fresh air intakes

03E2AC27-DDBE-49E4-BEDE-72E48C70A0B5.jpeg

ZX AC Bracket

BB531014-DD6D-4F6F-923F-8DE113C0D4CE.jpeg

ZX AC Bracket after sandblasting and paint

CC37686A-046D-4D8E-8B2E-A69F113F3D06.jpeg

That same ‘78 280z rear glass with an OEM rear window seal to fix this gaps in the corners. This was a major PITA to install. Super tight.

I also noticed a scuff in the shape of a Z logo. I think there was a sticker or paint on the glass and they didn’t take care getting it off. Gonna have to polish guy.

FDDD991A-502D-435A-BB06-D345E23F25B1.jpeg

Inner and outer (1970 version) weather strips

Edited by Matthew Abate
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Posted (edited)
12 hours ago, w3wilkes said:

Looks really nice! I'll bet you're starting to itch. I think I'd be afraid to drive it, looks more "polished" than factory.

My kids dinged the front left fender the other day with the door from our Subaru, so I am trying to embrace the concept of Wabi-sabi.

The goal here is a Z built from the “best” parts that will go on it, or, a Z that’s what Nissan could have made if they went all out in the beginning. Trying to keep the newer tech / styles to a minimum.

But yeah, I’m getting itchy.

Edited by Matthew Abate
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Posted (edited)

Side Project:

7836A47F-CCD1-424D-8086-BA29DE8F25B9.jpeg

I was able to find Nissan OEM versions of everything I need to overhaul the five speed. Luckily, I don’t need synchros, although you can still get them OEM from Courtesy Parts and the handful of Nissan dealers I called. I had to use a handful of places to get all of these, and I’m not 100% certain two of these are OEM despite reassurances from the retailer, but it wasn’t difficult to get it all in hand. Maybe 30 minutes on Google.

I dropped these off at the transmission shop yesterday. I have no idea how long it is going to take for him to get it done, but I’m hoping to have it back by the end of September.

Here's my parts list:

- 1x Main Input Shaft Bearing (PN 32273-N4800)
- 1x Main Input Shaft Bearing, Adapter Plate (PN 32273-36900)
- 1x Main Input Shaft Bearing, Extension Housing (PN 32203-14360)
- 1x Pilot Bearing, Input / Output Shafts (PN 32272-36910)
- 3x Needle Bearing, Main Shaft Gears (PN 32264-14601)
- 1x Counter Shaft Bearing, Front (PN 32219-E9020)
- 1x Counter Shaft Bearing, Adapter (PN 32203-E9800)
- 1x Counter Shaft Bearing, Rear (PN 32319-N4870)
- 1x Reverse Idler Gear Bearing (PN 32272-36910)
- 1x Front Cover Gasket (PN 32112-08U01)
- 1x Oil Gutter (PN 32137-E9000)
- 1x Front Seal (PN 32114-Y4000)
- 1x Rear Extension Seal (PN 32136-U010A)
- 3x Checking Spring (32830-20100)
Edited by Matthew Abate
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