Alternator

[Lex]

At what point do you need to upgrade your alternator? How do you decide on the AMP size?

[MonzaRacer]

As much as you can afford to buy, but honestly I sell the GM CSI 144 rated at 140amps, I can get you numbers from Pep Boys. It will fit sbc/bbc pretty easy.
And all you need is pulley to match what ever setup you have.

[H2Ogbodies]

Thats the alt. from a 94-96 Impala SS and has a 6" dia. case-won't fit a lot of engines without a couple mods. As for specifics, i would advise you to add up the max. draw of all of your components and I mean everything-then, figure you should be running an alt. that puts out 70% of that figure @ max. output. This way, you are assured of not taxing the charging system and overworking the regulator and overheating the diodes.

[hifi875]

you do not want to do a autozone/pepboys/ style alternator. if you need a high output alternator get a powermaster. One that puts out alot of current at idle, not max. the parts store alternators that say put out 105 amps usually only do about 40 or so at idle. a powermaster 140 amp will do 90+ usually at idle. electric fans/audio/vehicle electronics can consume alot of power and most of them need 12v to operate properly, not 10 or 11

[kryptik]

As much as you can afford to buy, but honestly I sell the GM CSI 144 rated at 140amps, I can get you numbers from Pep Boys. It will fit sbc/bbc pretty easy.
And all you need is pulley to match what ever setup you have.

I agree with this, had a Powermaster 12si series alternator before (140A) that just did not cut it. Yes, at high RPM the alt. would put out 140A, but at idle, with a Mark VIII fan and other accessories, the voltage dropped and the alt. just could not keep up with demand. Switched to a CS144 (140A) from National Quickstart and have never looked back. The alt. puts out A LOT more at idle and has all the goodies such as a digital rectifier/voltage regulator. It also survived this: https://www.pro-touring.com/showthre...in-your-Safety (see the third pic, that alt. still works great without a rebuild!)

All you will need to adapt a SBC is the correct pulley as MonzaRacer said, and you will also need an adapter wiring harness (cheap) and a metric bolt for the tapped alternator ear (I believe M10x1.25 or M10x1.50 but don't quote me on that)

Link to NQS, they are very nice and will hook you up with all the correct parts: http://www.alternatorparts.com/category_cs144.html

Link to wiring harness adapter (PN W1201/W1204): http://store.alternatorparts.com/cs1...r-harness.aspx

ALSO, when ordering a CS144 MAKE SURE it has the six-twelve mounting ears (180 degrees apart)!

[sam 74]

i use a Power Master 140 amp on my car, i have a decient amount of draw with electric fans, water pump, and other electronics plus the headlights at night so i went with the 140 amp and it works perfectly for my setup.

[MonzaRacer]

Strange I ran an AC Delco CSI 144 on my big block with the big stereo and had it on 3 different cars, all it took to fit regualt long pump brackets was a tweak with a cresent wrench to move upper mount up about 1/4 to 1/2 in, bolts are usually 10x1.5 and if going on big block chevy you will have to drill out bottom hole for big bolt.
been selling them for years even when I worked at AutoZone. put them on race cars, stereo cars and all that, no issues.
I have seen Powermaster alts quit very quickly, some have good luck some dont.
Use anything at your own risk. I install stuff that I have good luck with.

[SLO_Z28]

At what point do you need to upgrade your alternator? How do you decide on the AMP size?

Only when you absolutely need more power, and are over working your current one.


Everyone here underestimates how much power it takes to turn one of those alternators. It takes a lot of horsepower to turn an alternator the size of a 140amp CS144, and is completely useless unless you're running an EXTREME amount of electronics.

[68Formula]

As for specifics, i would advise you to add up the max. draw of all of your components and I mean everything-then, figure you should be running an alt. that puts out 70% of that figure @ max. output. This way, you are assured of not taxing the charging system and overworking the regulator and overheating the diodes.

X2

Don't know what year you have, but if you consider what was available back in the 60s, you can easily overtax the system.

Once you start adding things like a stereo and amplifier, electric fan(s), electric fuel pump, EFI, better headlights, power accessories, etc. you'll go over. Add up everthing (include options you plan in the future) and that will tell you what you really need.

Keep in mind the alternator is moving slowest at idle, therefore providing the least amount of output. Older wiring can also increase resistance adding load to the system.

[Six_Shooter]

Alternators, while they do take power to turn, electrically speaking a considerably larger alternator (amperage wise) will not take a lot more (horse) power to run.

Lets take a 140 amp alternator.

In a perfect world, it would always charge at 14.4V, regardless of actual load, so lets use that number for the time being.

Watts = E (Volts) * A(mps)

So 14.4 * 140 = 2016 Watts

1 HP = 756 Watts (745.699872 actual)

To find HP, we take the Watts and divide by 756.

So 2016 / 756 = 2.667 HP.

Now alternators aren't 100% efficient, so lets assume worst case at 50% efficient, which means that we need to multiply the HP figure we just found by 2.

2.667 * 2 = 5.334 HP.

This would only be if you actually pulled a full 140 amps out of the alternator, which would only happen at higher RPM anyway, where most of our cars wouldn't miss the 5 or HP.

This also doesn't take into account mechanical losses, but they are usually less than the electrical load anyway.

There's also something to be said about being about to produce full power from the engine, from having a solid and stable charging system as well. I have known of many cars that pick up power by putting a larger alternator that is capable of actually supplying the needed current.

[rrunner68]

My Powermaster 140amp Alt seized this weekend after about 2k miles. I'll be calling them tomorrow.

[SLO_Z28]

Disconnect your alternator and see how much you gain at the strip in MPH. I guarantee you a 140 amp alternator takes quite a bit more than 5 hp.

[68Formula]

Disconnect your alternator and see how much you gain at the strip in MPH. I guarantee you a 140 amp alternator takes quite a bit more than 5 hp.

Disconnecting the alternator is way different then just running a higher amp. You no longer have the parasitic loss due to the belt tension and alternator bearings, etc.. Even if you were running a 1amp alternator, you'd still have those losses. Keep the belt on, pull the alternator wire harness, and let us know the difference. I bet going from a mechanical fan to electric would more than make up for the extra alt load.

[speED]

Not sure of what accessories you are running, what year car, etc. But, keep in mind depending on your situation an alternator is not always the quick fix you think it will be. Voltage drop is a big problem with the older cars.