Bolt spacing outside to outside and bolt diameter which I think is 7/16":

This is 7/16"?

This is the spacing:hhL.Z

 

Let's blow this one up too:

 

From that picture I would bet that the front groove's outer rim is smaller than the 2nd groove. But if you say it isn't in real life I'll believe you. And, as I said in the text, I haven't measured my pulley quite the same way but will tomorrow, although I'm pretty sure from what I saw on the catalog that they'll swap. So, I'm betting I need to find a 351W, and I know where one is. Thanks!

 

Measure -around- the pulley, any difference will be multiplied by Pi.

 

Yes, but that isn't very easy on a day like today with the temp and wind we had when the pulley is mount and has belts on it. But Bruno can do it since he has it off.

 

Eddie - Sorry, but I missed your post yesterday. Or, more correctly, I saw it while out and about but by the time I got home we were on the next page and I forgot. Sorry. In any event, I didn't realize that Schottky diodes had achieved current-carrying capabilities that high. Back when I was heavily into electronics they were puny little devices used for their speed rather than capacity. Thanks!

 

I am not convinced. I am sure the diodes are rated way over the output of the alternator. There are 6 of them in there, and I don't know their individual rating, but I bet it adds up to way over 130 amps. You will notice the guy that sells the 160 amp unit sells a complete new alternator, not a upgraded 130 amp used unit. You will also notice the little asterisk down in the corner of the 160 amp unit that says pulley diameters and the rpm the alternator is turning has some part to play in the alternators output.

I still stand behind what I found in the previous post, the heat and saturation of the windings limits the peak output of the alternator.

 

Dave - I'm a little slow, so please humor me. I understand each and every word you used, including "saturation", but not the implication of them taken together. I'm not sure I want to ask a specific question as it may lead in a direction you hadn't intended. So, I'll just say "Please elaborate".

 

How does the fact that it is a "new", rather than a rebuilt alternator make any bit of difference?

Right on the first page of the epic FSB thread, it was asked how to change a 130A 3G alternator to higher output....


3G Interchange Facts. If you're thinking 3G read here. - FSB Forums

 

When you are messing around with coils, they store energy somewhat like a capacitor stores energy. There is a electrical field around any wire that is carrying current through it, a coil of wire will concentrate this field and adding metal to the coil will concentrate the field even further. This field as it gets bigger is taking energy to build. It can only build so far till it "fills up" or saturates. Then the current to the coil stops.

This is exactly how the ignition coil works, they close the points or the module completes the circuit, dc voltage is fed into the coil till it saturates and is "full". Then the points open or the circuit is opened by the module, and this built up field collapses, and rushes into the other windings in the coil and that travels out to give the spark.

The alternator is the same theory. Voltage is supplied to the windings, the regulator varies the amount of current in the rotor to determine the output of the alternator. The regulator can put more and more current in the rotor for more and more output, till the rotor coil cannot take anymore and it saturates. As it's working it's also getting hot, and just like a starter, hot windings have more resistance, so this starts to limit the current flow in the alternator windings also.

I did some searching on this, and it seems to be well known that the stock Ford 130 amp alternator is capable of outputting 160 amps as it comes from the factory. Larger diodes may make it more reliable, but I don't see how they suddenly make it a 160 amp alternator.

 

Dave - Thanks. That I understand, I think. So, is it fair to say that since the calculations I've done show that I need 95 amps in the planned configuration, anything more is overkill and the difference between 130 and 160 amps is moot? And, even if I were to add electric fans RJM's "160" amp unit would be adequate?

I'm still like that unit. I want a new alternator to maximize the probability for it to last many years, regardless of the warranty. And, at $130 it is less than many, if not all, other new units I've found. Further, it is only $20 more than the 95 amp unit, so upgrading to it looks to be an easy decision.

 

Go for the 160A unit then.
You will know the diodes aren't going to cook due to anything you throw at it.
(no winch, 2000W stereo, etc...)

I'm not trying to convince you -not- to buy the higher rated unit.

 

If you might go to electric fans, go ahead and get the bigger one. If you can afford it and want the larger one, it won't hurt to have it in there. You could even run it with the single v-belt, since you would never be using the full output of the larger alternator, unless you forgot and left your lights on and ran the battery down. Then you would probably get some belt squeal till the battery charged up a little bit.

 

... which is why I suggested a soft start (LRC) regulator.

 

I think you are beginning to understand me - overkill is good, and more is more better.

But, I realize the wiring harness for these trucks will melt down long before it distributes 160 amps for any length of time. It probably couldn't have done that new, and it isn't new by any stretch. However, were I to tap into the extra juice I would do so judiciously. () I already have moved the headlight current off of the harness with the relays. And I will run a new hot wire, suitably fused, to the sub-woofer which says it peaks at ~200 watts, so might pull 10 amps in spurts. Then there's the possibility of cooling fans, which would obviously have their own wiring from the battery/solenoid, replete with relays, temp sensors, etc. So the stock harness won't be handling anything beyond what it was made for, and even less in the case of the headlights.

But, that does bring up a subject - relays and fuses. IIRC someone, and probably Bill, had picked up a Ford relay and/or fuse holder that was under the hood. Was it Bill? I'd like to use "stock" components if possible. Might that have a place for the headlight relays? And, how big of fuses would it take? I've lost wherever that was, so should go searching for it, but if you know.....