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need help wiring my engine chevy 350

Guest glock240z

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Guest glock240z

I Have A 72 240z And I Just Put A Chevy 350. Im Having Trouble With The Wiring. Cant Someone Write Me What Wire Goes To The Starter , Alternator & Distrubitor.

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Not sure on the 240, but I just dissected a '75 280 harness. The starter wire is yellow to the sub-harness on the passenger side rear & stays yellow after.


The oil pressure is yellow/black stripe to the same sub-harness and solid green after.


The water temp is yellow/white stripe before the sub-harness (driver side front) and solid yellow after.


(This was cut & paste from my MS Word wiring doc I linked elsewhere here)

The Datsun alternator shows as having 4 wires connected to it:

A- White/Red- +12 volt output

E- Black- ground

N- Yellow- to voltage regulator

F- White/Black- to voltage regulator


The GM alternator has two wires connected:

Batt- Red- to battery

L- Red- to fuse panel via plug C220A


The Datsun uses an external regulator, and the GM is internally regulated, so there is less wiring involved. The GM regulator shuts down the alternator if there is less than 11.2 or more than 16.5 volts. Since the 1975 280Z used an ammeter, there is one less wire involved here. If you add a voltmeter (a good idea), use the wire at plug C220A.


The JTR manual states this setup may require the motor to be revved to about 2000 RPM for the alternator to switch on, at which point it will stay on. After reading the 1995 GM shop manual, I do not believe this is the case with the LT1 alternator if the “L” terminal is connected to a switched +12 volt source as is shown in my diagram.


EDIT- you must add in a 470 ohm resistor in the sense (small) wire to the LT1 alternator or hook it to an idiot light!


If you end up going with a different alternator due to adapting a Sanden AC compressor, the above wiring remains th same, you will just need to adapt a connector for the “L” terminal.


Can't help you with the distributor, as my LT1 setup has electronic ignition. From the looks of the Datsun harness & coil, I'm sure the wiring is similar.


As mentioned above a good investment here are the JTR book and a shop manual, as I am sure all of the above will NOT apply to a 240.

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  • 1 year later...
  • 4 years later...
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Huh did not know that about the LT1 alt. Looks like i need to get one of those resistors.


You don't need it. In fact it may CAUSE trouble. Run a small gauge wire, that's hot with the key on, to the field terminal of an LT1 alternator and it will work beautifully. Depending on how the car is wired you may need to put a diode in line. You'll know you need it when you turn the key off, and the car keeps running :-)

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  • 2 weeks later...

I went ahead and stripped all Datsun wiring out, put in a painless harness for a Chevy small block and mated all the Datsun connectors. Wasn't easy but it turned out outstanding. This may be something worth paying someone to do if you've never done it...prior to I had all kinds of electrical issues, post painless absolutely zero electrical trouble.

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