needed high amp alternator

[joshua dewitt]

have a 73 swinger small block with a/c and p/s, p/b....
my power master 90 amp will not cut it anymore, since car redo... have added dual electric fans, trunk mounted battery, nitrous, h4 head lamps, and msd, as welll as fog/driving lamps and a stereo... currently still running the dual belt design and factory alternator mounting with factory a/c brackets... what have any of you guys used from power masters rating chart if everything on, would need to have at least 150-200 amp alternator to be safe, all ready upgraded all the wiring to handle it, ,,, anyone have any ideas on application to look from? that doesn't break the bank.... one wire set up ok...

 

[BillGrissom]

By "to be safe", you must mean "insure the battery stays charged" since 200A is a lot of current to play with. What indicates that the current alternator is not doing its job? Is you battery running down so that you need to put it on a charger once a week? The only way to diagnose real-time is to use a clamp-on DC ammeter to measure various currents, but even that is hard since they vary w/ rpm, as fans come on, etc. Don't go by the current ratings on the fans, since that is often just the starting current surge, plus fans don't run all the time. I made some quick measurements on my modern vehicles (fans, fuel injection, ...) and see ~60A max w/ both fans on, so their 120 A alternators appear more than sufficient.

 

[joshua dewitt]

so, 120-150 amp you think would be enough? according to power master amp chart, it was putting me up there, that is why. my 80 amp power master is struggling, the volt meter drops 11.75 when fan kick on in high , the believe will need around 150 amp... is the dakota truck better choice that will bolt in , or should go with a gm unit.

 

[BillGrissom]

Different perspectives. I am OK w/ 11.75 V w/ the fans running as long as the battery stays charged. The battery is discharging under peak load, but I doubt that decreases its life. Some people expect the alternator to supply the peak load, meaning voltage holds at 14.3 V even with everything on. That would require a larger alternator. The main downside people see from the voltage dropping is that the (factory) headlights may dim slightly. In the near future, we may all have LED bulbs which regulate the voltage, so shouldn't dim. HEI bulbs may have regulators. For those old enough to remember 2 cycle 1970's motorcycles, many didn't even have a battery and their headlamps would vary greatly as they revved the engine at stoplights, which one had to do to keep them from stalling.

 

[jbc426]

I use a GM CS144 alternator on my '70 E-Body that's been mildly worked over a bit (ie) rewound, heavy duty bridge rectifier and upgraded wiring to handle it. It's basically the Mad wiring with a few deviations.

The alternator puts out 115 amps at an 850 rpm idle and over 220 amps above a fast idle. It pretty much bolted on with a $35 or $40 bracket adapter. I do have a single pulley driving it, and that is ultimately the limiting factor for output, but my system really doesn't need that much total output. I was after the higher idle output it easily provides.