[Philcol]

Changing to CSI electic water pump and duel electric fan set up (from Ramchargers)and need to know what amp I need to boost alternator to so it will handle the extra load. I have the std. alternator that came in my 79 T/A now. I know the larger the amp the more heat they produce and it will be close to number two header (using bracket that mounts alternator to right side head). May have to wrap header or shield. What would be min amps needed?

Phil

"dreamed I was wide awake........woke up and I was sound asleep"

[Philcol]

Changing to CSI electic water pump and duel electric fan set up (from Ramchargers)and need to know what amp I need to boost alternator to so it will handle the extra load. I have the std. alternator that came in my 79 T/A now. I know the larger the amp the more heat they produce and it will be close to number two header (using bracket that mounts alternator to right side head). May have to wrap header or shield. What would be min amps needed?

Phil

"dreamed I was wide awake........woke up and I was sound asleep"

[george kujanski]

Well, you are increasing your idle electrical loads with the addition of the electric pump. To me the major issue on proper alternator size is not necessarily the output rating (this is usually rated at 5000RPM shaft speed or higher), but how much output the unit has at engine idle speed. Alternators usually "cut-in" (start producing output current) at about 1100 shaft RPM. Near these speeds they produce much less than their max rating. Combine all low speed worst case loads, lights, pump, A/C, heater, stereo, etc, and you have a fair demand on the alternator at low speeds.

To close this discussion, the larger frame alternators (Delco 12SI), have better low speed output than smaller frame (Delco 10SI) alternators. Unfortunately, alternators are not described by their low speed output, but in general, you will be better off in your application with a 12SI. If I recall, these came in 84 Amp and 100 Amp. I would venture to say the 100 would still be better at low speed (cutin speed and max output are usually a trade-off).
I hope this helped rather than confused.......
Regards, Georg

[Philcol]

I can't run the larger alt if is longer or has more depth. I am too close to #2 header now and would probably hit the head also. I have the alt mounted low on the right side. I can rebuild mine to about 140 amp or so and guess I will try that.

Phil

"dreamed I was wide awake........woke up and I was sound asleep"

[chris spires]

According to the powermaster website, their altenator(100 amp) will cut in as soon as the engine cranks as long as it's using the factory 3 wire plug. If you use it with the 1 wire plug it will excite after it reaches 2400rpm, and will stay excited until the engine stops. I bought mine through summit for around $125, and it's a very nice alt, and it's dyno tested too.( comes with a dyno tag)

Don't blame me cause your chevy broke down, you should have bought a PONTIAC!!

[george kujanski]

The madelectrical.com site has a good article on alternators. BTW, on the above post I made a mistake that the larger frame alt is a 12SI, where actually that is a 15SI. A 12SI has the same frame size as the 10SI, but more output, better cooling, etc.

Regards, George