Alternator Change

[DohertyCM]

I am fed up with the motorola alternator with the external voltage regulator!

I have been thru 3 of them...and not only that they are hard to come buy much less have some butt-knucked alternator shop repair them for some out rageous price...! and troubleshooting usually leads to replaceing BOTH items...SUCKS.
(not to be misleading but the alternators have gone out during the past 18 months of operation)

Sorry am I ranting?

Look here is the deal. 1974 2.7 CIS motor...See picture below.....
Question.....What are the part numbers (if any) of the fan(and size) and fan housing......and which alternator would be a good upgrade for my car...

I do have an MSD box....and quite frankly run the car to its limit....
I know people have done it, but only make mention of it...no specifics...

This is the only place I know that will have answers....THANKS

[Walter_Middie]

DohertyCM,

I still have the external voltage regulator, and am doing fine with it. I'd say you need to either find a better shop to work on your alternator, or start doing it yourself. Here's a good article on troubleshooting:

Pelican Technical Article: Alternator System Troubleshooting

One of things it says is that if you have repeated problems, check your ground straps - alternator to engine, and trans to chassis.

I'm lucky here near Seattle, I've got an alternator shop less than a mile from where I work with a crusty old mechanic that recognized my alternator as one from a Porsche when I put it on the counter. He uses all these old tools and electrical consols that look like something right out of a Frankenstien movie. but he knows his stuff.

To answer more of your questions, here are some sizes:

1965-74/75.. 110 mm crank pulley..95 mm fan pulley
1976-77... 130 crank...83 mm fan ( may be 80 mm?)
1978-79....130 crank... 80 mm fan ( or was that 83 mm?)
1980-89.....120 crank....83 mm fan ( or was that 80 mm?)

for fan sizes / blades / air flow:
1965-74/75....245 mm / 11 blade... 1.3:1 ratio..1390 liters air/sec
1975/76- 77.....245 / 5 blade.......1.8:1 ratio....1265 l/sec
1978-79...........226 / 11 blade ...1.8:1 ratio...1380 l /sec
1980-89.........245 mm / 11 blade...1.67:1 ratio...1500 l/ sec

Turbos used the 245/11/ 1500 set up.

Interestingly... the later curved fans for the 964 were quieter (by being curved)...but resulted in lower flow:
-- 1.6:1 ratio..1010 l /sec (!).

fan belt sizes:
1965-75....9.5 x 710
1976-77.....9.5 x 725
1978-79....9.5 x 725
1980-on.... 9.5 x 710

It looks like you already have an 11 blade fan (and a cool collar, but I won't mention that), so I don't understand why you are wanting info on fan sizes.

The tech articles also have instructions on changing to an internal voltage regulator - so I'd look there first.

[304065]

Don't change to an internal voltage regulator.

The external VR is actually better-- HEAT is what kills electrical components. The internal VR, which is inside a fiberglass duct, two inches from the top of the engine case.

If you are experiencing failures, it's a connection problem. Do you have a ground strap between the D- and the case parting line? The powdercoating on your fan housing is probably insulating the alternator case from the engine.

[DohertyCM]

Thanks for the words guys really!!
Thanks for the info..!
Now to answer some questions, I have paid close attention to the grounding strap and it is grounded to the case at the split-line. I have paid close attention to the grounding strap at the battery as well. And when the alternator is working I do get a good voltage reading at the battery showing charge. When it works, it works well. Oh, and I do have the grounding strap to bare metal on the housing.
The problem I believe is age. with all of these components growing older, i think that they really only have so much life left in them. Vibration probably plays a large part in their failure.

I am not a purist...meaning that i am not against upgrading.... However I can help to think that a fan/alternator setup from an 80's model 911 would be a better upgrade, such as the 11 blade fan. And as I discovered these parts are not interchangeable - individually. they have to be dont as a set. But the downside to getting a later version is the thinner housing which sometimes cracks...
I ask the question also because of the alignment with the crank pulley. That has to be right on.

Not to mention that I had to have my friend machine the special nuts for the alternator from a piece of stock steel because I couldnt find them...1mm thread..
You dont like my cool collar?

[TR]

Hi
This is available in australia.

Alternator

[DohertyCM]

I am sending them an email now....I will let you know what they say.

Chris


THANKS!

[TR]

Hi I think I jinks myself.
went out to start my car and batteries all dead, think my altinator shat it's self. I'll probably be lining up to buy a new one too.
I will ring them for a price tomorrow.
Cheers

Terry

[DohertyCM]

That alternator from Austraila with shipping is 818 USD.

I think that might be a little steep for me.

I guess I will just have to find something else.