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Discussion Starter #1
I've spent allot of time looking around the FAQs for alternator upgrades and found zilch. Somone must have done it. I have the alternator below in the Bosch part number. In a Jeep with a winch, 65 amps is a bit weak. Anyone know a bolt in upgrade for this--between Ebay and other outlets I'm not having allot of luck/ The Bosch I have has only 2 wires--ignition and battery.:
Alternator - Bosch Style (12161), New, Bosch, 0-120-488-205, Case, A186125, Cummins, 3604448RX
 

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You probably need to contact a company that sells alternator to find a matching size with more amps. DB Electrical might be one to try. Your unit was fine for its original application. Also, all alternators aren't built the same. You might find one in your size for $75 or $300. How many amps are you shooting for? Most of our guys try to fit the factory alternator that matches the vehicle.
 

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Thanks Char--trying to get a least 100 amps (wished for 150 but thinking it may not fit). Nothing wrong with the Bosch on there now just want more electron flow...
 

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Be careful with peak output ratings. Alternators with a high peak rating and a small stator diameter have low output unless they are spun north of 8k.

Ideally you want something with a 140mm+ stator. Cummins pulley ratios typically spin the alternator at 3x the engine rpm for reference.

Here is a datasheet for the alternator you currently have.
66021631 - Alternator Product Details | Prestolite / Leece-Neville
 

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Be careful with peak output ratings. Alternators with a high peak rating and a small stator diameter have low output unless they are spun north of 8k.

Ideally you want something with a 140mm+ stator. Cummins pulley ratios typically spin the alternator at 3x the engine rpm for reference.

Here is a datasheet for the alternator you currently have.
66021631 - Alternator Product Details | Prestolite / Leece-Neville
Goat: Thank you so much for that--!
 

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You probably need to contact a company that sells alternator to find a matching size with more amps. DB Electrical might be one to try. Your unit was fine for its original application. Also, all alternators aren't built the same. You might find one in your size for $75 or $300. How many amps are you shooting for? Most of our guys try to fit the factory alternator that matches the vehicle.
 

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What alt mount are you using. On my 97 tj with 4bt I am using f800 high mount bracket. The alt for that is a j180 frame. If you are using a stock Jeep Wrangler tj or yj alt use a mid 90’s Dodge Durango alt. They came in 130 and 160 amp. The 130 uses the same wire hookup as 97-98 tj. The 160 uses a plug. The battery wire clip is different but will inter change among both alt. I have a130 amp sitting on a shelf that I no longer need. It has about 5000 mi on it
 

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Discussion Starter #8
Bigjon...mine is a 78 cj5. The alt bracket is the standard one that came on my 4bt. It’s a simple 2 wire connection, ignition and battery.not sure anything else would work there.
 

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Here's you a photo of a 4bt with the Ford high mount system installed. There are quite a few parts to that setup and it can be a bit expensive if you can't find a used one. Tennessee Diesel Conversions sell the complete parts kit for $1425. Not sure if that includes all the bolts or not. I have a complete Cummins parts list for that thing should you need it. It's a long list. That kit was never used on a 4bt but it will fit.
 

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Discussion Starter #11
Char--that is pricey! And my air box currently sits where that alternator is. Not sure I could go much bigger without extensive mods--the oil filter is one--it's quite close to my existing setup. THANK YOU for sharing that. --Bill
 

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That system is expensive. A few years back I priced out all the various parts and that $1425 is not a jacked up price. The AC compressor and 160 amp alternator are not cheap items. The bracket parts are pretty expensive. Even that belt tensioner is a lot. I bought a used kit off a 6bt several years ago without the AC or alternator. It was like $300 which was dirt cheap. There's probably $100 worth of bolts that hold all that stuff together. It is built like a tank. If the turbo is in the lower rear position it clears the AC compressor. I believe the oil filter clears too since the AC lines come off the side of the compressor. May need to change to a vertical oil filter but not positive on that aspect. If you wanted to look for a used setup, they were found on Ford and Freightliner medium duty trucks and school buses. Most of the ones found on buses didn't have an AC compressor but just a plate with a pulley to fill the spot.
 

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Discussion Starter #13
Luckily I have no AC compressor (well, "luck" in this regard--summers are hot!)--but I am looking at other setups.
 

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Well, there are other brackets for that large Delco alternator that don't include a mount for the AC compressor. You can find those far cheaper since it's not nearly so complicated. The alternators are a 21si, an update to that is a 22si, or the latest is the 24si. All those come in either a pad mount or a J180 which is what's used in the mid/high mount setup. Here's a list of the bracket and misc parts for that setup.
3910923 alternator support bracket
3900631 M8x1.25x25mm flange head bolt (attaches bracket to engine) 3 req
3903105 M12x1.75x150mm flange head bolt (attaches alternator to bracket)
3903210 M12x1.75 flange head nut
3910924 alternator brace
3052061 1/2"-13 x1" bolt (attaches brace to alternator)
3900630 M8x1.25x20mm flange head bolt (attaches brace to engine)
3918275 8 groove pulley for alternator
Here's a listing for 3910923 coming out of China for $34.99. New Alternator Support Bracket 3910923 fit for Cummins 6BT 5.9 Engine | eBay The bolts may cost you more than that. Here's the little brace for a whopping $9.91 Cummins BRACE,ALTERNATOR 3910924 | eBay and the pulley can be had in the $30-35 range. So with a little shopping you might have the whole assembly for around $100. The one sort of expensive part is that darn 150mm bolt. From Cummins it's around $25. Out of China $16.
 

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Discussion Starter #15
Char, might some of my existing bolts work on that (and my pulley). Can't thank you enough for your effort to detail that out--info there is like gold.
 

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I think if I were to do it over again, I would have the Delco 12si alternator that was on my CPL 858 4bt, and a common alternator, rebuilt to put out more amperage.
Instead, I installed a Delco CS144 out of a mid 90s Chevy police car that I had laying around from my previous Jeep project. The mounts were nearly identical. I just had to change the clocking on the rear of the alternator for the plug and install the 12si 8 rib pulley. It's max output is 140 amps.
I've been told by those with expertise with the internals of alternators that the CS144 is not the greatest alternator to install. But, it works well and I haven't had any issues with it for the last seven years since the 4bt conversion.
127064
 

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Yes, some of your existing bolts would probably work fine. The ones that attach the brace and bracket to the block are the same. The ones that fit the alternator to the mounts are different. The short 1/2" bolt you can find at any hardware supply, but that long bolt is a special item. There may be a possible option. That 150mm bolt which is 6" US could possibly be replaced by a standard 6" bolt. Everything on a Cummins is metric but that alternator was used on many other engines and the bolt was US. You'd need to see it a 1/2" which is 12.7mm would fit in the bracket. The only thing the US bolt may or may not be a flange head. Not sure if that is totally critical. Your existing pulley won't work. Those big Delco alternators have large straight shafts where the Bosch units have a tapered bushing that fits into the pulley. The pulley for the Bosch is part 3908560 shown below beside the 3918275 Delco pulley.
 

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Discussion Starter #18
Well I got it all ordered except the 3910923 bracket (the fellow in China is on vacation till 2/1). Excited to get a new project going--tks again.
 

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HA! I did order the pulley you specified b/c I knew the Bosch had to be different (hey, it's a Bosch--it has to be lol). So just got to wait for the bracket now----

On the photo from J10MIKE up there--thanks for posting that--real close to that oil filter yes? I like the idea of bringing it up a bit and I can see Char's method does that.
 

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HA! I did order the pulley you specified b/c I knew the Bosch had to be different (hey, it's a Bosch--it has to be lol). So just got to wait for the bracket now----

On the photo from J10MIKE up there--thanks for posting that--real close to that oil filter yes? I like the idea of bringing it up a bit and I can see Char's method does that.
Fairly close to the filter. But, doesn't touch the filter.
 
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