Can I use a GM alternator on my 73 Z?

[Bulldog Z]

I think my alternator may be going on my 73 Z. I just installed a set of super white Piaa driving lights, and the work great. I also put in some H4 halogen light for good measure. When my driving lights are on, my headlights seem to get dimmer. The driving lights have their own relay and switch which is a plus. My amp meter is still to the right of the middle line. I know that Z's have weak alternators to begin with. Do I need to upgrade my wiring harness to install the more powerful GM alternator?

Any thoughts?

[zbane]

You could just install a ZX alternator. If you run a quick search of the site, you will find that it is a fairly straightforward and common upgrade.

[Carl Beck]

The GM or ZX alternator will regulate itself to replace whatever current is being drawn from the starting battery, by whatever accessories you are using, at any given time. So the stock wiring should be fine in terms of powering the stock accessories.

As I recall - the fusible link in the 240-Z is 90Amp. So as long as the total amperage drawn by all accessories at any given time is less than 90Amp - I wouldn't see a need to "upgrade" the stock wiring harness.

It would however be sensible to add circuits independent of the OEM wiring harness - such as relaying the driving lights, huge amplifiers, and indeed adding the headlight relays etc. Additionally, a wire directly from the Alternator to the Starting Battery, so that the entire charging load isn't delivered through the stock wiring would make sense.

Since both the GM and ZX alternators are internally regulated - you would be disconnecting the OEM external voltage regulator - so you would want to use one of Dave's plug in resistors.... to cap off the old voltage regulator.

As I recall the ZX alternator is 65 Amp - where the OEM 240-Z alternator was 35/45 Amp... The ZX alternator is a direct bolt in, but you have to modify the lower alternator bracket to use the GM type. (you might also have to swap the V-Belt drive pulley).

FWIW,

Carl B.

[SteveJ]

In addition to what Carl said, I believe I have seen threads over at Zcar.com where people have used Z31 alternators. I don't think they needed to mod the bracket, but they would have still needed to jumper out the voltage regulator.

[Bulldog Z]

Thanks Guys for the comments. I think I will just use the ZX alternator. I think the GM model would be a bit of overkill.

Brad

[Walter Moore]

I waited until others commented on this thread before I said anything.

I have a 100A single wire alternator that I got from J.C.Whitney on my car. I had to make my own brackets, and even at that it just barely fits under the water pump inlet. As I only have about 200 miles on the car so far I cannot say for sure that this is going to work over the long haul.

I already burned up one alternator belt. That was after about 50 miles, then I re-adjusted and modified my brackets. So far the belt seems to be working, but only time will tell. (And I now carry a spare belt and tools with me at all times.)

The changes that I made to the electrical system consist of a separate circuit (In a watertight box) for my extensive high wattage headlight/driving light/fog light/electric cooling fan circuit, direct connections from the alternator to both my new lighting circuit and the battery, and a volt meter since the direct connection from the alternator to the battery bypasses the amp meter.

As for the factory voltage regulator, I removed it and just covered the connectors heavy plastic.

I hooked up the standard fuseable links at both the starter and alternator, so the existing wiring harness is still in use, but the new overblown accessories are separate. (My lighting/cooling box has a #4 AWG wire direct from the alternator, that feed three 30 amp fuses, one for each primary circuit.) My new wiring is all over sized for a car, but I am an electrical engineer and just couldn't bring myself to use normal car sized wire.

Frankly, I really hesitate to tell anyone else to use a G.M. style alternator on a Z car because I have serious reservations about my home made bracket staying aligned over the long course of time. I guess there is a thread here somewhere about a company that is selling single wire, high amperage alternators in a standard Nissan alternator case. I may eventually scrap my existing setup and go that way.