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wingwalker

Wiring hell--a question

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I've been working on my 280 Z and will test-fit the engine (carbureted Vortec 350) once I am able to bundle up this bird's nest of wires.

 

Because the guys at Vintage Air suggested I mount the compressor on the passenger side, I have my alternator on the driver side. And that means the wire feeding the alternator needs to run a long way. As you see in the photo, I was about to send it back to the firewall, across and then forward to feed the alt. But a few minutes ago I noticed that if I run it along the inner side of the cross-member, it is a pretty straight (and much shorter) shot. I have drawn in an arrow to the wire in question. Once that's decided, I can begin re-wrapping the harness.

 

(By the way that relay closest to the firewall will be either for the fuel pump or for the electric fan--I haven't decided (and I'll take feedback on that issue, too).

Wiring puzzle.jpg

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Okay, without any feedback encouraging me to take the unconventional path, I will carry this feed-wire the long way around. But to avoid voltage drop, I have ordered 8-gauge to replace this 10-gauge wire. When It arrives, I'll route it around the front and be done with wiring hell. Finally.

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You can run the wires pretty much any way you want.  All things being equal, obviously a shorter run of wire is more desirable than a long run.  I originally considered running my main alternator wire along the path you were considering, but it ended up being slightly shorter on my setup going down the driver-side frame rail and across the firewall.

 

Other factors to consider are "neatness" (if that's important to you), durability/survivability, and maintainability.  A lot of solutions are easy to initially implement, but become a bitch later on when it's time to work on them and/or replace them.

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Richard and JHM--thanks. I appreciate the input. As  I mentioned, I ordered (from Jegs) a more robust 8-gauge wire kit, and when it arrives, I'll finish that bit.

 

Right now I confused as hell about the wire to drive the tach. I have a blue wire separated and labeled for that, but I'm pretty sure it's wrong. I want to get this right, because I really don't want to cook the tach.

 

 

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Richard and JHM--thanks. I appreciate the input. As  I mentioned, I ordered (from Jegs) a more robust 8-gauge wire kit, and when it arrives, I'll finish that bit.

 

Right now I confused as hell about the wire to drive the tach. I have a blue wire separated and labeled for that, but I'm pretty sure it's wrong. I want to get this right, because I really don't want to cook the tach.

 

--------------------

 

Okay, I just tested the  blue wire to the tach resistor, and sure enough, they have continuity. So, I'll attach the blue wire to the negative on the HEI when the engine goes in and see what happens. The JTR book says to turn the brass adjustment on the back of the tach 45 degrees, but the text doesn't mention which way. I'll leave that step until after I have the car running, since this may have already been done (it previously had a SBC in it). Getting closer.

 

 

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Posted (edited)

On my V8 swapped 260, I ran the tach wire from the GM HEI straight to the stock tach (with the JTR-recommended resistor inline), and it's been working fine for years.  I thought the adjustment was only needed for a 240 tach, but my memory could be failing me.

Edited by jhm

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The OEM tach in your 280z should work just fine hooked up to the HEI output. There should be two black - white wires if you are using OEM, If not then refer to the manual for that harness. Look at the JTR book to make sure you have them correct. 

 

I ended up yanking my wiring and going full race car with my own relay and fuse boxes and switches. 

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Grog and Twisted46,

The alternator is 65 amps and I won't be running a huge stereo amp, so I believe 8 gauge will be okay. It think total it will be about a five-foot run. At the most, six.

And I have been using the JTR book, but because this car had been hacked--not just wiriing, but on many other levels, the book is for me just a starting point. I think I have the correct wires for the HEI. At least I hope so.

 

In a separate post today, I show some photos of us stuffing the engine onto its mounts. Feels good to have most of the wiring behind me, and the engine now bolted to the front mounts. (The transmission right now sits on a box. Fitting the rear mount will be next.)

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There are some calculators you can use but I would seriously consider 6g as your biggest load will come when the car sits for a while and the alternator has to charge the battery. I blew a fusible link by letting and alternator charge an almost flat battery. You will likely never have an issue with 8g but it only takes one unlikely event for hell to break loose.

 

https://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

 

Yes POs are the biggest problems when working on old cars. I spent weeks looking through the 260z wiring diagrams and probing with a multimeter. I would start at thr tach and work your way to thr end of the loom if you think wires have been crossed or replaced.

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