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Getting your early 240Z tachometer working with an MSD 6 Series ignition.

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This post is an effort to spare others the confusion I endured trying to figure out how to get my Z's original tachometer working with my MSD 6AL. A cursory search of HybridZ uncovered similar confusion, these two threads are prime examples:

 

http://forums.hybridz.org/showthread.php?t=77434

http://forums.hybridz.org/showthread.php?t=77651

 

Most people seem to just dump the original tach, but mine was still working fine, so I saw no reason to toss it. New 5" tachometers are a hundred bucks. The tach adapter from Summit is less than fifty.

 

Obviously, the tachometer signal on the MSD is something entirely different than the current triggered signal the OEM four-wire inductive loop thingy. The solution is an MSD Tach adapter. The confusion I ran into was which one to buy, and how to wire it, as the Z is just a tad different than the examples in MSD's diagrams, and all the people cheap enough to not just buy a compatible tach seem to be very poor at documenting how they get things to work.

 

The tach adapter you need is the 8920. NOT the 8910.

 

To wire it up:

Find the two ends of the tach inductive loop over near the coil. One wire is green/white, the other is black/white. I advise you to use something to check continuity and make sure you have the correct two wires, as they really aren't two wires, they're opposite ends of the SAME wire.

 

Remove the 8920 tach adapter from the package. Throw away the instruction sheet. Neither diagram applies to the Z.

 

It has four wires coming out of it:

 

Black - ground

white - trigger

Red - option1

violet - option2

 

Now, to get the tach working:

 

1. Take the black/white wire near the coil, and hook it up to an ignition switched 12V (hot when key is on).

2. Run the RED wire from the tach adapter and connect it to the green/white wire.

3. The white wire from the adapter goes to the MSD's tach output.

4. The black wire goes to ground.

 

That's it. That's all there is to it.

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Guest bastaad525

I have that tach adapter and still wasn't able to get the stock tach working, even when I had the N/A motor with ZX distributor.

 

 

I'm just curious though, would this exact same wiring setup apply to the turbo motor if installed in a 240z? I've already got an autometer tach but wouldn't mind having the stock tach working.

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Not at all.... read the first post in this thread, that's what needs to be done.

 

I've already done that, and it did work, its just not reading accurately, at idle (900rpm) my tach is reading about 200rpm.

 

before i added the MSD, the tach worked perfectly. the car runs extremely well with the MSD/blaster 2/pertronix set-up, but would like the use of my tach.

 

I apologize if I'm not understanding you properly, I'm just looking for other options as to why the tach would not read accurately.

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On my early Z with a V8, I use the TechnoVersions TachMatch with the MSD 6 trigger signal output as the input, and its conversion from 8:6 to make the tach read correctly. This is with the early Z current-trigger tach, but it works on the later Z voltage-trigger tachs too.

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Do these insructions apply if I am using the magnetic pickup? I have a ZX dizzy without the e12-80 module in my son's 72 240z. The red and green from the dizzy are connected to the green and violet of the MSD 6T. The switched B/W is hooked up to the switched (red thin wire) from the MSD. The G/W and the other B/W are connected together.

I was told By MSD to use the 8910EIS because I am using the magnetic pickup???? The MSD still gives the same output to the Tach connector right? Glad I saw this post!! You guys know everything about these cars!!

Thanks,

Mike

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Do these insructions apply if I am using the magnetic pickup? I have a ZX dizzy without the e12-80 module in my son's 72 240z. The red and green from the dizzy are connected to the green and violet of the MSD 6T. The switched B/W is hooked up to the switched (red thin wire) from the MSD. The G/W and the other B/W are connected together.

I was told By MSD to use the 8910EIS because I am using the magnetic pickup???? The MSD still gives the same output to the Tach connector right? Glad I saw this post!! You guys know everything about these cars!!

Thanks,

Mike

 

THREAD REVIVAL!

 

This is a question that I wish had been answered, because I am about to dive into this tonight.  I just dropped a built L28 into my '72 that I picked up from someone.  It already has the ZX dizzy installed and was previously running with this MSD 6AL... I just want to make sure I get the tach right.  From what I've gathered so far it sounds like I need the 8920... I've searched through multiple sites and nothing difinitive yet... any input or direction from the gurus?

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My sincere apologies for digging up something so old, but I could use some help.  I'm having the same issue as 72_NorCal...
 

This set up atleast got something to register in my tach using the tach adapter and wiring as stated, but at idle my tach says its doing 150-200rpm.

any ideas?

 

Any idea what might cause this?  Bad Tach? Bad Connections? 

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I still would like to know if I need the msd 6al. I have the tach adapter 8920. From reading the first post it doesn't say. Just says the tach adapter 8920. However when looking at the instructions provided with the adapter it shows a msd 6al as well.

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