Is the stock 305 alternator enough for a 383? if not what amp etc would you need?

 

The alt has no way of inspecitng the bore and stroke of the short block. It will be perfectly happy no matter what the CID.

 

I just figured the overall drain on the system would be more with the 400 starter and all... I am going to at least get a bigger battery.

 

Use a "mini-starter". It consumes less power turning a 400 than the stock POS does turning a 305. You'll find, if you actually install a 400 in your car, that the stock one is inadequate to turn it over anyway; I struggled with that for years before I finally wised up and got the right thing. What a difference.

But, regardless, the size of the alt is irrelevant. As long as it can charge the battery back up after it starts the car, it's adequate.

 

Alan,

I have found that the cheap rebuild at all of the major chains are pretty worthless. If you can afford to do it right, buy a new one.

RB,

What about replacing my stock alt. with a higher output amp alt. though?

I'm not exactly sure what I've got right now, but I know that it is rather gutless. I have some additional cooling fans hooked up, and if I'm running those, the lights, stereo and such, to roll down the window is T E R R I B L Y S L O W .

Too much drain on the electrical system.

Is there a decent, higher output altenator out there we can use?

Oh, and the battery is fine, and the alt. charges at about 14 volts or so, so I'm pretty sure my electrical system is OK.

 

It's pretty tough to get an alternator of any particular "rating" from a parts store...

Here's what happens at the rebuilder. Cores come in, and are sorted into piles of Delco SI-10, Motorola, etc. etc. Presently it comes to pass that they need, let's say, SI-10s. So, they send a tear-down grunt out to the pallet, with a work order to tear down 250 of them. He whoops out his air ratchet and begins to tear down; case fronts in this barrel, case rears in that one, stators in another, fans in another, armatures in another, bridges in another, etc. etc. Each barrel / basket / pallet goes to its respective steps for the operations it requires; cleaning, painting, testing, slip ring turning, etc. etc. etc. Presently after all of those prep steps are complete, they are reassembled; the assembly grunt pulls a case rear from that pallet, a diode bridge from that one, a stator, a voltage regulator, a brush set, a resistor, etc; and assembles it. Then he grabs a case front, a spacer, an armature, a fan, etc., and assembles them. Then he puts those together. It is tested, and is determined to function. Voilà, the finished product; into the box it goes, it is now a 7120.

Now..... what parts determine the electrical rating of an alternator? The stator and the armature, and to some extent the regulator and resistor, right? And, what part is the rating stamped on? The case front, right? Now from the description of what actually happens at a rebuilder, how is it possible that they have the slightest clue what the "amp" rating of their product actually is???? The answer of course is that they don't. Each alternator is a totally random collection of parts, with the "rating" stamped on it completely disconnected from whatever parts are actually in it. But, they will sell you a "104 amp" alternator, and charge you more for it than a "67amp" one; or they'll sell you one for a "85 IROC", and it costs more than the one for a "78 Olds 88"; but as far as they actually know, they're all the same!!!! Thay are all built randomly out of the same pile of cores, and the "rating" is completely divorced from anything electrical about the product! They are simply taking advantage of the uninformed nature of the buying public, to make an extra easy buck.

If your alt continues to put out 14V while you're rolling your window up (another word for "under load"), and the voltage doesn't drop, then you won't be able to make any improvement by replacing it. If the alt output voltage does drop, then you can improve your electrical system with an alternator upgrade. Most of the time you can't, you'll see if you measure the alternator's output directly while it's loaded, that the voltage doesn't drop: i.e. the alt is putting out enough current to keep the voltage from sagging.

 

RB,

Yeah, my voltage drops, big time.

I'm very unhappy with the alt. I have. So I'm thinking of upgrading, but don't want to have more of this kind of result.

Any suggestions?

 

Is that the voltage on the gauge, or the voltage at the alternator output terminal (big red wire)? the car's wiring will cause voltage drop between the alt and the gauge, even if the alt is working perfectly; and if that's the case with your car, no alt in the world will make a difference.

Although, there are a couple of things you can do to help it out.

The alt has 2 terminals besides the big red one. The one closer to the big one is the idiot light ("Choke" light in our cars) terminal, which is also the way the alt "knows" that the ignition is on. The light bulb supplies current to it, to start the alt when the engine begins to run. By lowering the resistance of that circuit, but not so low that the alt can power the ignition through that resistor (which would make the car keep running when you turn the key off), you can increase the current in the field windings (armature) which increases the magnetic field inside the alt which raises its capacity. You accomplish this by putting a resistor in parallel with the bulb, which will allow more current through the field windings, which will boost the alt's output capacity.

The other trick is to change the point where the regulator samples the voltage. The way the regulator works, is it simply allows more or less current through the field windings, up to the maximum possible as determined by the circuit resistances, at which point whatever the stator can put out is the alt's "rating"; and it adjusts the armature (field) current to whatever it has to to keep the output voltage at its set point of around 14.4 volts. The regulator "looks" at the voltage on the terminal farther from the stud for this value. In most of these cars, it's hooked right straight up to the stud with a 6" piece of wire. If instead, you hook that terminal up to a point inside the chassis of the car, somewhere way downstream of all the wires and switches, you can force the alt to put out a great deal more than 14.4 volts at its terminal, as it then will try to keep the voltage at the point where the "sense" terminal is connected at 14.4 volts. So the alt might produce 16 or 17 volts at its output terminal if it has to in order to keep that other point at its "set point". If you run a car like this, you can overcharge the batt and destroy it, so you need to be careful about where you hook that up to.

OBTW - I know people who use those alternators, without their diodes of course, to generate 208V 3-phase. Believe it or not, it can produce about 2 kVA of that type of power long-term without burning up. The alt is inherently a 3-phase source, it's just rectified to DC by the diode bridge, so most people never even realize that.

 

Well you just answered another question of mine for me!

Some how or another the original power source for my fan pooped out on me. I'm not exactly sure how or why, all I know is that it did and I wasn't in a place where I could spend a lot of time figuring it out.

So I ran a wire from an empty fuse to the fan.

Now since then I've added a remote switch and another fan. I just kept using the same power supply source. When I shut the car down with the fans on, the car will continue to run for a few seconds...........



Fans off when I shut off (fans off and stopped spinning), no problems. Oh, and I have a relay in there too!

 

I don't know where RB gets his information but I hope to hell I never get a unit from where he refers to. Fact is REPUTIBLE remanufacturing facilities DO in fact know what they are rebuilding. The CS series alt for instance uses the same hybrid IC regulator for all output ratings, only the stator is different. You can easily convert a 65 amp to a 100 by changing the stator, or a 100 to a 140 by doing the same. The only different IC reg Delco offers is a self exciting one wire unit. To infer that AC-Delco remanufacturing supplies incorrect replacement units is absolutely ridiculous. If you buy a 105, you get a 105. There may be some hacks out there, but reliable sources like NAPA or AC-Delco simply do not do this. As far as the current rating you choose in most cases for a car with a lot of power accessories figure a 100 amp unit to be a good choice. Driving habit also have a lot to do with what you want, if its a Sunday drive with little accessories a 65 amp would be fine, city driving at night with a lot of electrical load go with a 100. Whether its a 65 or 100 as long as the load does not exceed its output and in most cases it won't the battery should be maintained well enough by the alt to provide reliable starting. Remember, the alt only keeps the battery around 70-80% of it's rated capacity in ampere-hours. They are NOT battery chargers. A lower amp unit will increase the longevity of the battery, a high output one shortens the useful life. Hope this was of some help.

 

Go visit a rebuilding plant, any rebuilding plant, some time... go see for yourself how they do it. Think about how, in a high-volume / low overhead / price competitive / mass market operation like that, how much hassle it would be, and how much it would cost in inefficiency, and how few people are willing to spend what it takes to get that level of service when they'll go shopp[ing to save $2 on the price of their replacement alternator, let alone $200. It would be economic suicide.

As I said, go look at one, all of a sudden those "reputable" suppliers won't be so holy any more.

 

Actually I have. About 10 min from where I live is one of the largest AC-Delco authorized remanufacturing facilities on the East Coast. They do everything from auto radios to digital dashes to ECM's. It's nothing like you say. Parts are sorted, then routed to the appropriate line for repair. Most items have a predetermined batch of replacement parts installed, as well as any parts upgrade that is deemed required by GM. Once thats done it goes to testing and only after it meet new equipment testing specs is it packaged and shipped. That in fact is where the difference is between OE components and the aftermarket junk. Thats why an AC reman alt is $200vs. chain store for $50. NAPA is the same way when dealing with thier suppliers and it is why many large chains try to duplicate NAPA's parts procurement and distribution. I won't be foolish and say that there is not junk out there, I know firsthand there is, but to make a blanket statement that most reliable companies knowingly market incorrect or substandard replacement parts is nonsense. To say that AC-Delco/Delphi, Motorcraft or Mopar don't care about quality control with thier supplied parts is even more ridiculous. I know it's popular today to trash companies with blanket statements but in reality a lot of effort is put in by a lot of people to maintain a level of quality. Canyou imagine for a minute Delphi selling 65 amp units in place of 105's? I know a couple of lawyers who would love to sink thier teeth into that.