Datsun Roadster Forum-311s.org

Phil: you need to either limit the output of the alternator to what the wiring is rated for or upgrade the wiring.
If you have a high output alternator or higher than stock, what are you powering with the extra capacity?
I always advise a protecting device at the alternator output terminal to limit the amount of current the stock wiring can draw under a fault condition.

Nissanman wrote: Tue May 15, 2018 7:53 pm Phil: you need to either limit the output of the alternator to what the wiring is rated for or upgrade the wiring.
If you have a high output alternator or higher than stock, what are you powering with the extra capacity?
I always advise a protecting device at the alternator output terminal to limit the amount of current the stock wiring can draw under a fault condition.

I did the 3-wire GM alt conversion as described in the TechWiki. That alt is rated at 60A-65A, but the instructions say only a 30A fuse is needed. I also thought that the actual amp output will only be what the system needs to charge the battery, run the lights, etc. instead of the fully rated output.

Am I misunderstanding something?

Thanks.

No misunderstanding, all that sounds good for the upgrade.
My point was that under a fault condition a high output alternator can fry 30A wiring very quickly so protection for that scenario is very important as you would appreciate.
You can always fit a modern power distribution system for anything non-stock.
I have drawn up a typical schematic to show how this can be safely done: -

What nissanman said! It's a good safety measure. I was experimenting with my amp clamp and the alternator was putting out around 3 amps at idle and bumped up to about 7 amps at 2k rpm and higher and then trickled back down. Battery was fully charged before start up. Alternator regulating at 14.2 volts.
The alt. I got is rated at 40 amps. The test graph that was printed out showed a peak output of 56 amps 6000 rpm.

I put 2 fuses on mine, one at the alternator and one on the starter. Both 30 amp fuses.

Anyway. I got the alternator from db electrical. search Kubota Alternator 16231-64010 16231-64011 16231-64012

I chose a rear post, they come in all kinds of flavors. From what I learned, the denso 93mm alternator is really common for industrial applications. There is a ton of China new not reman alternators sold by various ebay/internet stores. none of them are real denso just copies. Some people advertise them as a Chevy 1 wire racing alternator.

The mounting ears seem to be the same distance apart as a Delco alternator and lend to being a very approachable alternator for conversions.
I needed only a slightly longer lower mount bolt and a metric bolt to thread into the alternator for the top mount. I also needed to go to a smaller drive belt. I used
Napa 25-7385 which is a gates belt.

The fancy pulley I found, which in my opinion is not necessary but looks cool is 3.5" not 4" like I had thought. Jones Racing Products (WP-3104-A-3.500) V-Belt Drive Pulley for Alternator, 3.5" https://www.amazon.com/dp/B003TQ89Z0/re ... -Ab1AYBNKB

Here is a site that has a lot of information about the alternator and pulley sizes.
http://www.metroautoinc.com/Download/download-home.htm

Hope that helps some.

I am not worried about the wire size being a problem....Mine is the 35A version. I soon will have my Volt meter conversion installed and add a second jumper wire direct to the battery or starter post through a Circuit Breaker.

I am still not seeing the information about the rotor shaft diameter. I found 3 different "standard" pulley shaft sizes. 0.642, 0.669 and 15 mm

15 mm

Thanks

Nissanman wrote: Tue May 15, 2018 7:53 pm Phil: you need to either limit the output of the alternator to what the wiring is rated for or upgrade the wiring.

Always a good idea!
My Alternator is rated at 35A continuous, but can put out 65A at 6000 rpm under high load conditions....3000 engine RPM

Nissanman wrote: Tue May 15, 2018 7:53 pm If you have a high output alternator or higher than stock, what are you powering with the extra capacity?

NOTHING
This is lowest Amp rating I could find in small single wire alternator.
I am not very concerned about having to wait for the high load current rate to settle down before driving....it takes less than 30 seconds.
If the continuous load is over 35A, than the wiring is going to be overloaded and start overheating.....BAD

Nissanman wrote: Tue May 15, 2018 7:53 pm I always advise a protecting device at the alternator output terminal to limit the amount of current the stock wiring can draw under a fault condition.

I agree completely.
The limit needs to be for surge rating, not the constant current rating more like a 50A fusible link at the alternator.
Nissanman: I just noticed you suggested 100A maxi Fuse......

That 100A would be for an aux. power distribution loom as drawn. Not meant for the original loom which is not shown on the diagram.

I was going to put in a gm alternator. This looks nicer. Sorry if I am dense regarding the wiring of this application. Not yet clear to me.

1) I assume the big nut on the back is the ground. If so, no problem.
2) Not sure about the other connection. It appears to be a 2 wire connection with posts at 90 degrees from each other. Is one of those connected to the battery with a connector I buy at the local auto parts store?

3) And in an unrelated concern. Am I correct that the same 1 1/4 inch trimming of the lower bracket on the engine block that was done with the GM application is the same here?

Again, I apologize for having to have things so spelled out for me. I am really hopeful to get my 67 1600 on the road soon. Mark

NO, THE BIG NUT IS THE CONNECTION TO THE HOT.
The internet is yoour friend, just search GM alternator wiring for pictures

I see that now. Insulation around that big nut. The ground to any other nut on the body of the alternator. The two pronged plug is ignored? Mark

Usually there is a small threaded boss for the ground.
You may or may not need to hook up the two wire connector.
You will need to check, but one goes to the large lug and the other goes to the ignition switch through either a resistor or light to limit the current.
If you don't hook them up, you might have to raise the engine RPM to energize the alternator first thing when started.....should be good until you shut off.

I believe the Denso and GM alt installs are similar. The GM alt upgrade is not limited to Datsuns. Google GM 3-wire alternator to find quite a few posts, pics, drawings, and YouTube videos. Here's mine (click image to get larger view).

• Lester Part No. 7127-3, 63A

• Terminal #2 Sensing (red wire) attached to insulated BAT post on alternator, same post that you connect another wire to POS (+) of battery.

• Terminal #1 Field (black wire) not connected and taped off.

Could this alt be installed on the driver's side? I actually like the left side mount despite the heat.
Linda