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How to install a 93mm Denso Alternator

by toptech and others

I decided to to replace the giant Delco 10 si alternator that had been retrofitted to my 1500 decades ago. It was a reliable old beast that still works fine but it looked out of place hanging off the little inline 4. So when eBay emailed me a flash sale coupon for 15% off anything i pulled the trigger.

These alternators are equipped on Kubota tractors and many other industrial applications. They are also popular as mini alternators for race cars and can be found easily often described as Chevy mini race alternators or Denso mini alternators.

Performance wise this one is rated at 40 amps. The Delco was rated at 35 amps. Not sure on weight (maybe 4-5lbs?) but definitely weighs less than the big Delco. I would think it can handle high rpm just as well as the old alternator if not even better due to its compact size.

On to the pictures. I apologize for the poor quality pictures. The lighting in my garage is not that great and it was hard to take decent shots. I tried taking before and after shots from the same perspective but I was a little off.

Side by Side Comparison
Engine Bay Pics
Engine Bay Pics
Engine Bay Pics
Engine Bay Pics

Yep! I had done that with the Delco already. I actually have 2 fuses, one directly off the alternator and another at the starter. I figure the 40 amp Denso should not anger the roadster gods too much over the Delco (perhaps it is even a good will gesture haha!, but regardless always a good thing to mention.

Yes working perfectly. My install was very easy, but that may have been because the alt. Mount had already been modified to fit the Delco style alternator. Otherwise it was a bolt in affair. Wiring was also very simple for my car with a charge light (no ammeter) 1 wire to charge lamp, the other a key on 12v to excite the alternator and last the "big" wire to the battery(starter) The only other change I had to make was go to a shorter drive belt, although the stock one would have worked it was putting the adjustment at the far end of the bracket.

I need to find the PDF but I found something from Denso claiming it can handle high RPM's and tested to 12000 rpm. When I get home I'll look for that in case I'm off on my facts lol.

I also did find a fancy billet 4 inch pulley but it cost more than the alternator did. I decided to risk it. For what it's worth my old Delco 10si had a pulley nearly the same diameter and it never had any problems. I figure this one should be able to handle high RPM's no problem.

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.

Your right the denso and Delco do wire up the same EXCEPT that you need to hook terminal 2 sensing wire to a key on 12v source other wise the the denso will think it's always "on" if hooked to a constant power and will cause a parasitic drain.

GM Alternator connections

Denso Alternator connections

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.