New to 911's have alternator size question
 

Hi to all, I'm new to 911's and new to this site. I bought a 1975 targa being converted to a race car for the 3.2 and trans in the car. The previous owner never got the car going. I removed the engine and trans and was trying to get the alternator fan hub mounted up the alternator. I found the hub wouldn't mount up. I find the 3.2L engine has a early fan housing model 901-106-101-5R with a 50 amp alternator.

My question is, with all the electrical things in my 84 911 Cab (car the 3.2L and trans is going into) like heater fans, power seats, power windows... should I find a 930-106-102-3R (or 4r) housing to have the larger alternator or will a 75amp which is I believe the biggest I can get for my housing be sufficient?

Any help would be appreciated.

I question the reason for keeping power seats/AC/etc in a race car.
You should be lightening the car as much as possible.
So...the 50 Amp unit would be good if you get rid of the extras...if not...get the biggest one that fits.
Remember....the regulator must match the alt!
Bob

Bob,
I'm putting the engine from the "race car" into a weekend ride 84 Cab. Sorry, I should have been more clear.

I'm trying to figure out if a 75amp will be big enough or if I should upgrade housings and go back to what came in the '84' which would have been a 90 amp alternator.

OK...didn't get the road car idea...
If you can get the correct housing and a 90 Amp Alt...go for it.
With that setup, you will have good charging even with all the accessories on.
And in the end...a stock looking engine...which is probably worth more.
Bob

If you change the alternator, you must change the fan housing too

Alternator
 

According to the charts I've seen, the housing I have will take up to a 75 amp alternator. I'm currently looking for a new housing to go up to the 90 amp my car should have.

I believe that as the amperage of the alternators grew, the alternators themselves grew in length. Which required that the fan housings be machined deeper, so the pulley would end up over the crank pulley. As long as the fan diameter and the housing ID are right for each other, it is this alternator depth mounting which needs to be adjusted. And the casting numbers on the fan housing aren't a whole lot of help, although I think the shift from 901 numbers to 930 numbers may at least be a way of knowing what for sure is not going to work (unless some machine work was done for longer alternators, or you are willing to shim up a shorter alternator in a housing bored deeper.

901.XXX.XXX accepte only short alternator. There is a short alternator who provide 75 or 90 amp ?

Below is what I'm using for a reference as to what alternator/housing combinations work. According to that chart, my housing will fit a 75amp alternator unless I'm reading something wrong. It appears the 910 and 930 castings have the same depth from the lip to alternator mounting face and take the same size alternator.

http://forums.pelicanparts.com/uploads18/Picture11298466326.jpg

75 A is fine, don't worry.

Cabmando - what a great chart.

It shows that as the alternators got longer, the shroud depth got deeper by an equal amount. Which is how it would have to be to keep the pulleys aligned.

Well, thanks to everyone who replied. I bought the proper housing and alternator after considering all my options. I felt it best to go with what Porsche put in the car.

Walt,
I found that chart here on Pelican in another thread.

Not sure if all the part numbers on that chart match up to PET...I have been looking for a post-84 Carrera housing and fan and PET shows 930.106.012.000 (fan), 930.106.006.07 (housing) and 964.106.251.20 (strap).

It looks like the measurements are pretty good though....

Dennis

On the last post, the differences are Carrera, with no studs, turbo with the 2 studs for the coil and the 964 Turbo which is a different housing.
Bruce