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#1281126 - 08/07/12 06:54 PM What alternator amperage should I use?
justnuts40 Offline
member

Registered: 03/16/03
Posts: 155
Loc: Illinois USA
I have a mopar street rod that needs a lot of juice with power windows, electric fan, power seats, ect, ect. Would it help the battery to use a big amperage alternator. What sizes are out there? Any help?
Thanks, Tony


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#1281127 - 08/07/12 07:24 PM Re: What alternator amperage should I use? [Re: justnuts40]
Dodgem Offline
master

Registered: 03/21/08
Posts: 5664
Loc: Ontario, Canada
I got the 120 amp denso kit works great need a bigger line alt to battery though at least #6
http://chucker54.stores.yahoo.net/mabwealbrkit.html
This is a BB kit

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#1281128 - 08/07/12 07:57 PM Re: What alternator amperage should I use? [Re: justnuts40]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 26003
Loc: Lincoln Nebraska
Quote:

. Would it help the battery to use a big amperage alternator.


Yes ideally you want to keep the batt topped off all the time and the only time it is draining (except for cranking) is when the alt cannot keep up with the demand and the batt fills in then at higher speed when the alt charges better or when the accessories are switched off the alt charges the batt back up thru the bulkhead circular route. This shortens the batteries' life over time Many options, the OE appearing 78 amp one from an 85? M body, there's the huge Mopar Leece Neville 100 amper which I think is only available with big block bracketry which may not look right in an open street rod then the pictured Denso alts which are reportedly good. Many prefer to run the alt directly to the battery which renders the ammeter inaccurate (the Madd bypass). I prefer to clean all connections and only bypass the 2 large main in/out brass terminals/wires on the bulkhead (fusible link in/out to alt) with Nacho's bulkhead bypass. If the ammeter is close to 12o'clock most of the time then excessive current is not passing thru the system/bulkhead & if I'm going to run alot of high powered accessories which would run thru the bulkhead then I'd relay then right from the source (the alt) which only increases the alts' duty cycle which you cant get away from & that's its job but most important it keeps the current away from the bulkhead/interior. Some of mentioned accessories would only be on for a short period of time, windows/seats
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#1281129 - 08/08/12 05:40 PM Re: What alternator amperage should I use? [Re: RapidRobert]
goldduster318 Offline
pro stock

Registered: 01/19/03
Posts: 1244
Loc: Farmington Hills, MI


Delco 12SI. They work awesome...at minumum they are 78 amps, and they charge very well at idle. Very cheap. You can get chrome or powdercoated cases anywhere. Even better is they have an internal regulator, and anyone can take it apart. I switched from a reman 78 amp mopar alternator to the one seen here (78 amp 12SI for a 1985 305 Firebird) for $75 total, and my lights no longer dim at idle, volt gauge never moves. I even used the same v-belt.
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#1281130 - 08/08/12 07:31 PM Re: What alternator amperage should I use? [Re: goldduster318]
71yelladustr Offline
super stock

Registered: 12/25/10
Posts: 796
Loc: Missouri U.S.A.
There is something about seeing a GM alternator on a Mopar that makes me want to They do work though. I got a 120 amp Denso on my car and it works well. I have an electric fan and electric water and fuel pump. Holds a charge just fine. A mopar 78 amp just wouldn't keep up. I would go for a 120 amp+ alt in your application too. More charging capacity is way better than not enough.
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#1281131 - 08/08/12 07:51 PM Re: What alternator amperage should I use? [Re: 71yelladustr]
goldduster318 Offline
pro stock

Registered: 01/19/03
Posts: 1244
Loc: Farmington Hills, MI
Quote:

There is something about seeing a GM alternator on a Mopar that makes me want to They do work though. I got a 120 amp Denso on my car and it works well.




I always found this funny because Denso is owned partially by Toyota. I've never been sure why installing a USA made GM part (many Mopars have GM Saginaw P/S pumps and steering columns) is bad, but a Japanese part is ok on an old Mopar? We use 10SI/12SI Delcos on everything, street rods, muscle cars, 40's/50's cars in 12V conversions, farm tractors, etc. Install and forgetaboutit. If you use a denso, for God's sake get one with an internal regulator, the mopar regulator (especially the ones you get from parts stores anymore) are garbage.
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#1281132 - 08/08/12 09:14 PM Re: What alternator amperage should I use? [Re: 71yelladustr]
justnuts40 Offline
member

Registered: 03/16/03
Posts: 155
Loc: Illinois USA
Thanks for the info. Do you have a year or part number from the alternator your using? Does it have a built in regulator? What wiring did you have to change?

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#1281133 - 08/08/12 09:22 PM Re: What alternator amperage should I use? [Re: justnuts40]
ahy Offline
master

Registered: 01/22/07
Posts: 6050
Loc: IL
Another option is the MOPAR "high amp" option from the mid-late 70's 100+ amps, excellent idle output, heavy. If you have AC, options are limited since the brackets have fixed swing and extra bracing. The "big MOPAR" is a good option with AC... Denso is better without.


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#1281134 - 08/08/12 10:08 PM Re: What alternator amperage should I use? [Re: ahy]
challengermike Offline
mopar addict

Registered: 08/16/03
Posts: 1052
Loc: Amherst,NY
I use a GM CS120 alt. They come in 120 and 140 amp versions. There easy to mount to the factory brackets. One off a buick grand national 1986 or 1987 will work. They also can put out alot of amps at idle from what i have been told.

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#1281135 - 08/09/12 05:40 AM Re: What alternator amperage should I use? [Re: challengermike]
DGS Offline
enthusiast

Registered: 07/08/05
Posts: 367
Loc: Graz, Austria
I use a 120A alternator from a 2000 Audi A4. idle output is 70A which is sufficient for 99% of all cars.

Installation is pretty easy but you need a different swing arm (made my own) and some other small thing (longer bolt, wire a diode or charging lamp into one wire etc.). It is internally regulated too!


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#1281136 - 08/09/12 10:41 AM Re: What alternator amperage should I use? [Re: challengermike]
jbc426 Offline
top fuel

Registered: 03/01/07
Posts: 2284
Loc: West Coast, USA
If you don't "update" the rest of your electrical system using the basic principles discussed on Mad Electrics website, you are risking some serious problems by running a higher output alternator with all your additional electrical load.

I ended up using an upgraded (rewound w/ heavy duty bridge rectifier & regulator) AC Delco CS 144. The comes in Escalades and some full-sized pick-ups etc. It essencially bolts right in with a simple adaptor. It puts out 115+ amps at idle & over 200 amps above a fast idle.

However, the more difficult & time consuming part of the complete electrical system upgrade job, is to wire the car to be able to safely distribute and protect the wiring system.


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