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justnuts40
member


Reged: Mar 16 2003
Loc: Illinois USA
What alternator amperage should I use?
      #7326495 - Tue Aug 07 2012 06:54 PM Attachment (36 downloads)

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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Dodgem
master


Reged: Mar 21 2008
Loc: Ontario, Canada
Re: What alternator amperage should I use? [Re: justnuts40]
      #7326546 - Tue Aug 07 2012 07:24 PM

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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RapidRobert
circle track


Reged: Nov 20 2003
Loc: Lincoln Nebraska
Re: What alternator amperage should I use? [Re: justnuts40]
      #7326603 - Tue Aug 07 2012 07:57 PM

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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live every 24 hour block of time like it's your last day on earth


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goldduster318
super gas


Reged: Jan 19 2003
Loc: Farmington Hills, MI
Re: What alternator amperage should I use? [Re: RapidRobert]
      #7327772 - Wed Aug 08 2012 05:40 PM



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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'70 Duster 470hp 340/A-833/8 3/4 3.23 Sure-Grip


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71yelladustr
mopar


Reged: Dec 25 2010
Loc: Missouri U.S.A.
Re: What alternator amperage should I use? [Re: goldduster318]
      #7327928 - Wed Aug 08 2012 07:31 PM

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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71 duster 440 4 spd dana 60


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goldduster318
super gas


Reged: Jan 19 2003
Loc: Farmington Hills, MI
Re: What alternator amperage should I use? [Re: 71yelladustr]
      #7327964 - Wed Aug 08 2012 07:51 PM

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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'70 Duster 470hp 340/A-833/8 3/4 3.23 Sure-Grip


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justnuts40
member


Reged: Mar 16 2003
Loc: Illinois USA
Re: What alternator amperage should I use? [Re: 71yelladustr]
      #7328115 - Wed Aug 08 2012 09:14 PM

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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ahy
master


Reged: Jan 22 2007
Loc: IL
Re: What alternator amperage should I use? [Re: justnuts40]
      #7328132 - Wed Aug 08 2012 09:22 PM Attachment (21 downloads)

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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challengermike
mopar addict


Reged: Aug 16 2003
Loc: Amherst,NY
Re: What alternator amperage should I use? [Re: ahy]
      #7328226 - Wed Aug 08 2012 10:08 PM

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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DGS
enthusiast


Reged: Jul 08 2005
Loc: Graz, Austria
Re: What alternator amperage should I use? [Re: challengermike]
      #7328420 - Thu Aug 09 2012 05:40 AM

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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jbc426
1970 Cuda Black Series


Reged: Mar 01 2007
Loc: West Coast, USA
Re: What alternator amperage should I use? [Re: challengermike]
      #7328654 - Thu Aug 09 2012 10:41 AM Attachment (23 downloads)

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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1970 Plymouth 'Cuda
1968 Plymouth Barracuda Convertible 5.9 Magnum EFI
Here's a little video by Mr Angry about the 1970 'Cuda http://www.youtube.com/watch?v=VzHxZ2f7HwY


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