Crankshaft Pulley Upsize?

[Nailhead]

Can I put a larger crankshaft pulley on a 230? Like, bolt one on?

My truck won't charge at idle unless I give it a little choke, and I'd like to turn the alternator (retrofit GM one-wire) a little faster. The pulley on it seems to be as small as can be fitted, so I guess the only alternative is to upsize the crankshaft pulley. The idle speed is already set a little high, by the way (I don't have an RPM for it).

The guy I built the truck with has an M37 with an IH 240-6 in it, and that thing has a crankshaft pulley the size of a pie pan. He has no low-speed charging issues.

[Beast]

I would be worried about over spinning the water pump. The water pumps are some what fragile with the bearings and seals and are becoming harder to find. It would probably be easier to have the GM alternator rewound for low RPM use. Find an old school alternator rebuild shop in your area and talk to them, they can usually build it to exactly what you need. I had one done several years ago for my big off-road trail Jeep with a low RPM set-up because at trail idle speeds I needed to be able to run everything without killing the power.

[brute4c]

Not one I ever heard of...

Sounds to me like you need a larger output alternator or the alternator needs work. Alternators charge at idle...thats the reason they went to them over generators, which do not.

[Don Cavey]

Agree, the alternator should charge at idle. A smaller pulley on the alternator will spin it faster too.

Are we talking the stock M715, Jeep 230 engine alternator???

[rboltz]

He's talking about the modern "one wire" alternators. I put one on my M-37 because I needed 60 amps for the radios rather than the 25 from the stock generator. Those alternators need more rpm's for some reason as designed. The M-37 won't charge at idle either with the "one wire". It's not a alternator fault, it's the way those "one wire's" are designed.

[brute4c]

Interesting...though sounds like a defect in design to me...

[Von]

Could yank the one wire and put a 12s on it. I'm using the 12s off the 85 GMC 3/4 ton engine donor vehicle. Once I start the truck and goose the gas a little to excite the alternator it puts out 14+ volts at idle.

Pretty easy to wire up, just gotta add a Gen light and/or resistor wire for terminal 1.

AlternatorHarness3 by kerry walker, on Flickr

[brute4c]

That looks like the solution...nice job including the wiring info!!

[Nailhead]

He's talking about the modern "one wire" alternators. I put one on my M-37 because I needed 60 amps for the radios rather than the 25 from the stock generator. Those alternators need more rpm's for some reason as designed. The M-37 won't charge at idle either with the "one wire". It's not a alternator fault, it's the way those "one wire's" are designed.

No, it does not like idling at traffic signals, etc., and it takes quite a stab at the throttle to get it charging after start-up. Otherwise, it works fine.

[Nailhead]

Could yank the one wire and put a 12s on it. I'm using the 12s off the 85 GMC 3/4 ton engine donor vehicle. Once I start the truck and goose the gas a little to excite the alternator it puts out 14+ volts at idle.

Pretty easy to wire up, just gotta add a Gen light and/or resistor wire for terminal 1.

AlternatorHarness3 by kerry walker, on Flickr

Thank you for that-- I'll give it some consideration.