alternator not charging enough

[emanscharger]

Hey guys..looking for some help..I have a 70 charger..just got it running..I have an 800 horse hemi in it..I have an electric fuel pump and twin electric fans..I put in a powermaster alternator..I don't think it's charging enough..at idle with the fans on it's at 12 volts..with the fans off..13.2-13.5.   can anyone tell me what the alternative is for anothert alternator? I bought the powermaster because it's a direct fit..question 2  I ran the motor for about an hour today..can you mess the motor up with only 12 volts in the system? I have a 6al box and full msd ignition..msd tech says 12 volts is enough?   please help!

[Paul G]

Do a search for "Denso alternator". It is a very popular upgrade to use a new Denso alternator from a late model dodge truck or van. It has a 2 wire hook up that can still use your existing regulator. Maybe someone will chime in and let you know if it will work on a Hemi. The articles I have read about it have been done on 440 motors. 

[Chryco Psycho]

a smaller diameter pulley on the alt may speed it up enough to maintain enough power at lower rpm

[Paul G]

Here is the link for the Denso swap if your interested.

http://cuda66273.proboards23.com/index.cgi?board=Tech&action=display&thread=1081309590

[2Gunz]

Fans generally have a 30 amp fuse in them. So lets assume they really draw 25.

Thats 50 amps already.


The MSD Takes (quick google here on this, and I have no idea exactly which one you have) 1 amp per 1000 RPM

So at Idle lets say its 5 amps for the hell of it.


Fuel pump (once again googled)

race pumps appear to take 8-20 Amps to run.

So lets say yours is 15


Other Random junk.....

Lets say 10 Amps.


For a total of 80 Amps.

Ok so...

Few important things to remember.

1. Alternators are rated at MAX output, NOT Idle.
So an 80 Amp Alt might only give you 40 - 50 Amps at Idle.

2. Fans are on or off. So they draw full power or dont. It doesnt go up or down with engine speed.
Which is a killer at idle when your power is low.

3. Upgrade your wiring. Charger wiring is generally just enough to work when it was new.
and in 40 years and some updates and forget it.

4. electronics as a general rule like high power (AKA your ignition)
Im not talking overkill here. 12 volts is "enough" but 14 is alot better.

My car has an electronic ignition and at 12 volts it doesnt run very well.
At 13+ its happy as a clam.


I looked at the powermaster website and I assume you got the 80 amp alt.
If thats the case you need to upgrade.

I would suggest you try to find something in the 140 amp area.
At idle that will prolly put out 90 amps.

That will allow you to run your car and sit in traffic with the headlights on and not have to walk home.

Oh and voltage wise I would shoot for 13+ volts with the car running at idle.

Oh and UPGRADE the Alternator wires if you havent already.
You can never have to big a gauge wire.

Many topics around here on that sort of thing do a search.

A quick read...

http://www.enjoythedrive.com/content/?id=10078