Alternator upgrade question

[EVIL72]

 Well I just upgraded my coil to a pertronix 45,000v flamethrower II and now the car will die randomly when in idling in drive or reverse unless I turn my idle up high, then it only dies when I turn on my headlights.
 I've always had the dim headlight thing at idle and I'm sure I'm running the stock amp alternator, what's that 40-50 amps? I'm cleaning all the connections just to make sure, and I'm going to take the alternator down to have it tested, but I think it's time to upgrade.
 My car just has a Mallory unilite distributor, and coil above, and around a 650 Watt stereo system.
 NO electric fans, or A/C, etc
 What amp rating Alternator will do the job, without going overkill and causing electrical problems with the stock wiring. 
I've seen some 65amp and 75-80 amp alternators but there all square backs 
 Thanks for any help.

[MEK-Dangerfield]

Even a stock setup shouldn't be this bad. Maybe they'll find the alternator is weak. Have you tried a new voltage regulator yet? I did go with an 80 amp alternator that I found on E-bay. I think you if go bigger than that, you'll have to upgrade the wiring to handle the current.


  Mike

[Bullitt-]

EVIL, I'm not sure that Alternator/battery is your problem & this is why. Years ago I was on my way home at night when I realized my alt. was not charging. I drove 50 miles with just battery running parking lights & headlights when I had too. When I got home the Battery was dead but she had made it. Once I had a '73 Duster 340 which I jump started without a battery in it & drove about a mile to a friends house.
Don't know what your problem is but I would look first at the block to body ground strap, then maybe the ignition power starting at the ballast resistor, maybe change the $5. resistor for good measure.

[ShelbyDogg]

You are going to have to go to the bigger alternator. They are all square backs unless you have to have a round back for OEM judging. You can get those rebuilt for high amperage but at a high cost.

For now try a square back 65 amp from an auto parts such as AutoZone. It's returnable and CHEAP if you find the right application. They list a 72 Chall 340 65 amp Alt for $44.

If you also noticed in the wiring diagrams, 60 amp cars used a bigger black charging wire from the alternator with some wiring changes. I never use anything less than a 10 guage wire for this. Compare a 10 guage to the factory 40 amp alt charge wire and you'll see why the factory wires melted.

[GoodysGotaCuda]

I'd bypass the amp gauge.
http://www.madelectrical.com/electricaltech/amp-gauges.shtml

And im running a $25 junkyard 90amp Denso alternator that works off the stock voltage regulator. 

[MEK-Dangerfield]

Another thought, if this should be some kind of voltage loss from going thru a firewall connection... I have read on here about people connecting a wire from the alternator output to the "+" terminal of the battery. This should be a decent sized wire(10 or 12 gauge), and run it directly, don't go thru the firewall. I imagine you could hide this wire creatively along the front of the engine bay. Some day when I get to it, I'm going to do this for a little insurance.

  Mike

[ShelbyDogg]

Mike, When you do that, make sure that you include a piece of fusible link wire in the connection at the battery or starter relay.

[MEK-Dangerfield]

Mike, When you do that, make sure that you include a piece of fusible link wire in the connection at the battery or starter relay.

Thanks Rob. 

[Bullitt-]

 

[EVIL72]

 UPDATE: Ok, I took the alternator down to Autozone and the alternator tested good. But that still doesn't give me any real information. I still have no idea what amp rating it is, or if it is putting out enough power at idle, which I still think it's not. It actually is a square back, I guess I never noticed it.
 So I cleaned all the connections from the alternator all the way to the firewall, I also found the field wires on the alternator to be loose so I removed them to look at the brushes and found them to be pretty dished in.
 Then I started it (at a faster idle) and it went into reverse, then I turned on my headlights and it still ran, then I hit the highbeams and the motor instantly went dead!
 So I'm figuring I'm getting farther at least it runs with the low beams on.
 I noticed I didn't have a gound strap from the motor to the firewall so I added one...no change
Tried a new voltage regulator...no change
 Then I decided to have a look at the back of the ballast resistor and found that the connection with the wire in the spring inside is totally broke in half, but once I replaced it with a new one the motor won't even stay running in reverse with the low beems on now.
 
 I went to autozone to get a 65 amp SINGLE groove alternator but they only had 50 amp ones, went to a couple more autoparts stores and no one seemed to have a 65 amp single groove alternator....  
 I looked at Summit too, anyone seen any...?
 Also thanks for everyones input. 

 

[ShelbyDogg]

Use the Autozone website and check the different stores around you till you find a double groove.  The store itself can tell you which other stores stock it. Also, use different applications till you find one in stock.  New Yorker, LeBaron, Cuda, Challenger, Etc.  Lots of vehicles used that alternator and there is a double pulley in each store but you have to have a counter person willing to help you.

Rob

[EVIL72]

 Thanks Shelbydogg, the problem is I need a SINGLE groove 65amp alternator, I know I can use a double groove, but since I don't have A/C it just looks like I'm missing something when you look at it. I may still have to go this route as a last resort, I'm just trying to get the right one.

[ShelbyDogg]

Try the double first to see if it fixes the problem. If it does, use the AutoZone "loan a tool" to pull the pulley off of yours and the new one.  Pull the alternator apart using the 3 small-headed screws then take the top (armature -half) to an auto parts store with a press, then put it back together. 

You just can't press the pulley on with the alternator assembled.

Just get the cheapest 65 amp single or double pulley LIFETIME ALT that they have. IF your lucky enough, you'll find the one for $25.00.  (I just can't remember what vehicle it fit)

[EVIL72]

 Thanks for the ideas 

[wiging19]

The bearings on my current Alternator if burning out.  I've always gotten the 65 amp alternator since I have power windows, air conditioning and special interior light package.  I was looking at alternators online and noticed CSK/Shucks auto had 100 amp alternators available.  I know a few of you mentioned it might be over kill for most cars.  Why?