MSD 6AL - 280ZX Dizzy - 240Z Tach

[CoastGuardZ]

I am in information overload here and I am looking for setups that have worked for others. I have searched and searched and with all the info out there on all the Z sites I can't determine what actually worked under what circumstances. I mean seriously, you can prove and then disprove the theory of relativity within a post or two in some of these threads.

The short of it is that I am in the process of connecting an MSD 6AL with MSD Coil to a 280ZX Distrubutor in a '72 240Z with the original tachometer.

The more complete version: I recently picked up a somewhat used Rebello 3.2L with triple Mikunis and have already put it in place... along with replacing the entire driveline... ACT Clutch, T-5, STi R180 LSD, Wolf Creek Halfshafts. The ZX ignition module was not being used in the previous owners setup and it was running the MSD instead. The wiring for the MSD seems pretty straight forward... because there isn't a module the green/purple goes straight to the dizzy which is wired for it. The coil is straight forward.

I "think" I need the 8920 Tach Adapter... but in a thread somewhere somebody was swearing up and down they were using the 8910... and then there is the 8910EIS. And in a few spots people are saying 8610, which MUST be a typo because that's CSB crank trigger kit. I'm pretty certain I will need one, but which?

I remove the ballast right? Where do those wires end up? Aren't they going to the tach? Is this where the Adapter comes into play?

Also, what is this about the ignition signal running through the Tach and if a wire somewhere is disconnected it won't start?

I plan to connect the MSD up tomorrow and fire this baby up with or without the Tach, I just want to know that a solution is on the way.

I've actually got a brand new Mallory Uni Lite in a box that will eventually find it's way on this motor, but I want to prove the engine works in this car with it's last known good setup before I start swapping parts.

Thanks!

[beermanpete]

If you need a tach adapter it will be the 8920. There is instruction on the MSD website. Go here and enter 8920 to search for the instruction sheet: http://www.msdignition.com/instructiondownload.aspx

The early Z has a current triggered tach, commonly refered to as a "4-wire tach" in the Z forums. It is true that if the tach were to become disconnected the car will not run. However, this is no more likely than the car not runnig from a bad connection elsewhere. Using the MSD igniton and tach adapter removes the tach from the primary circuit for the igniton and will prevent this particular problem.

[tlorber]

I can't answer specifically what you are trying to do, but I can tell you what I did.

I am running an electronic dizzy from an '82 ZX in my '73. I had my tach rebuilt by North Hollywood Speedometer (For around $175.00) because it was not working properly (even before the electronic dizzy). They basically remove the guts of the tach and replace them with more modern components, which they say will work with any wave form in triggering the tach. This allows you to use whatever tach/triggering system you want and the tach is more accurate than the 38 year old electronics, which were probably not all that accurate when new.

I have bypassed the ballast resistor, because I don't need to worry about frying points. I believe the '73 tach is slightly different from the '72 but once the internals are replaced that shouldn't matter. As far as the MSD portion, that should not matter either since it is downstream from the dizzy.

[CoastGuardZ]

Thanks guys! I sat down with the wiring diagram for the Z, the MSD and the 8920 and made a composite that made more sense now that I can visually see that the Tach is removed from the ignition circuit by the MSD box... so no worries there.

tlorber- I hadn't even thought about being able to have the stock tach rebuilt/upgraded... and I think you have changed my path! I've been researching aftermarket products and just haven't been 100% happy with any particular brand. I think the Autometer SportComps look great, but I really wanted to keep all the warning lights and indicators in the gauges without modding brand new $$$ gauge. So now I will give some serious thought to having the tach and speedo rebuilt.

So for now I will connect the MSD and coil up and attempt to verify the new drivetrain and just go "rpm's by ear" since I intend to start the full teardown for paint and body this summer.

Thanks again guys!

[CoastGuardZ]

In case someone else comes across this post in need of it, I am uploading the wiring diagrams I sketched up. If anyone sees any inaccuracies please feel free to set me straight

MSD 6AL - 8920 - ZX Dizzy - 240Z Tach - v2.pdf

[CoastGuardZ]

Update: I wired it up as indicated in my previous drawing and she runs great! No tach as suspected and I plan to hold out for the tach and speedo rebuild.

[sklein239]

This is great info, thanks all. One question...on the original wiring of the 4 wire tach on a '72 Z, where is the "12V" wire connected to? (my wire is yellow/redstripe)

[beermanpete]

This is great info, thanks all. One question...on the original wiring of the 4 wire tach on a '72 Z, where is the "12V" wire connected to? (my wire is yellow/redstripe)

The wiring diagram shows it connecting to the green wire coming from the ignition fuse (20A).