fan housings same number but different

[47silver]

I have 3 fan housings with the number 901 106 101 5r.
2 of the housing need a good cleaning, the other is perfectly clean and is like new.

But the 2 dirty housings are the same, the cleaner 1 is different.
The difference is the depth of where the alternator mounts.
Where the bolts of the alternator penetrate the housing the thickness on 2 of the 5R's is about 3/8ths of an inch but on the other 5R the housing is about 3/4 inch thick.
This thicker housing pushes the alternator out too far so that the fan is not in the housing.

My original was the thinner mount, the thicker mount was one i purchased that was cleaned and powder coated.
My questions:
Is the thicker housing one that was not machined properly?
Is there an alternator that fits this housing which means it is a good housing?
Can i get the like new housing machined without compromising the structural integrity?

thanks

[Flat6pac]

The thicker flange was made for the earlier Bosch alternator, the thinner was for the Motorola alt. the thinner can also be used to update the alternator to the Paris-Rhone onboard VR. These pieces are all pre78 units.
Bruce

[djdsc]

I ran into this when switching out a 5-blade fan on a '77 911S. There are many instances where Porsche kept the same casting number on a part even though there were subtle changes over time.

[47silver]

Then my best bet would be to get a thinner bosch alternator for the thicker flanged housing that is in great shape.
the fan should work i suppose.


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