Quick question for anyone with a 911 engine handy. I need a measurement of the amount the alternator spindle or fan pulley sticks out from the fan housing.

Thanks,

Adam

Check www.rennlist.com , that is a very active 911 board and I'm sure you'll get help there!

About 1.25"

this is a '70 engine though

Im not sure if other fan configs (5 blade etc) had different dimensions

Hi Tim,

Thanks for the picture, but I didn't explain what I was looking for I think. I need the amount the spindle or pulley or the face of the fan,sticks out from the fan ring. Trying to figure out how much I need to have shaved off the inside of the fan ring to get my alternator to fit.

Thanks,

Adam

I got 1.122" on my 70 914/6 with 11 blade fan.

Forget my last reply then. I'm still not certain I understand though. On mine, the face of the fan is flush (more or less) with the outer fan ring (the housing, yes?).

If I read this correctly, then the measurement Tim and I gave for our respective motors is what your looking for if the fan face is flush with the outer fan housing ring?

Ok, I can probably figure it out with that then. My alternator blew, and the FLAPS ordered me one in that was supposed to be identical(I paid extra for next day service), well I go to install it and the the fan ring where the alternator studs go through is too thick so I can't get the nuts or air guide on the back. I need to figure out how much needs to be machined out of the ring, but don't have my old one to compare how it mounted. I'm pretty sure having the fan pulley and crank pulley lined up properly is A Good Thing™.

Thanks for the help guys. I'm going to go put it together and eyeball how much I need to have taken off. So the blades of the fan are flush with the ring then?

Thanks,

Adam

Not the blades of the fan, but the face of the fan hub is within .002-.005 of the outer housing ring. Close enough. The fan blades themselves are recessed from the outer ring.

Gotcha. I just put my alternator and fan back together and here's the pic I took.

Obviously a little more than what it should be.

Gotcha. Now I'm clear. Definitely looks like you're sticking out too far. Or at least farther than a stock 914/6 2.0 motor should be.

Can you just replace the alternator studs?

I could extend the studs, which would at least allow me to get nuts on the back, but with as much alternator as I have sticking out the front, I think I'd toast something (alt. bearing?) in pretty short order as the pulleys wouldn't be close to aligned.

Hi Adam, I just ran into this after the idiot powdercoater ruined the fan housing on my early 930. There seem to be different combinations of fan housing and alternators depending on the year. In my case I had to have 10mm removed from the fan housing where the alternator mounts. I could post a picture of my old housing if that would help. Good luck! -John

Yes there are different combos of fans housings etc..
One of the problems with getting a replacement alternator is that the early alternators are NLA, the later replacement is slightly different , as you found out..

Its to late now, but often it is best to have your alternator rebuilt, and returned to you. It is a "known"

You can kinda see in the pic I posted the fan blades project to the radius of the fan housing.

Not too late now. I had actually dropped the alternator off at a local shop to have it repaired. They were missing the triode that burnt out, so it couldn't be repaired on Friday, I told them to go ahead and get the parts and fix it, but they've got the alt. and won't open till tues. This won't work to get me in my car in time to burn rubber across our wonderful nation, so I had the replacement overnighted only to be out core and $40 for expedited shipping for an alternator that won't fit. bastards. I figured it was worth it to get the car running, and I could sell the rebuilt Bosch when it was finished and make up for at least the core charge (Labor & parts was ballparked at $55).

I can see that in the picture. Another data point to help my machinist buddy fix this up (if he ever gets back from vacation.
For future posterity in case anyone else runs into this problem here's a pic posted on Pelican, the straight edge is apparently flat at the points where the arrows are.

adam,

this won't help much, but i ran across this thread on pelican when i was having problems with my alt. it really doesn't answer your question about machining the housing. but it seems the answer is to get the correct alt for your housing.

good luck!!

So that's where it is. I found it yesterday, and then when I realized that I was having the same problem couldn't find it again. Thanks for posting it. Sounds like at least someone successfully modified their housing to fit the bigger alternator, although hogging it out by hand doesn't seem to be the answer. The poster's unit looks pretty much identical to mine, although mine was supposed to be externally regulated (it was also supposed to fit). I haven't seen any internally regulated porsche alternators, so I don't know how to tell the difference. Here's what mine looks like:


The internally regulated units Porsche switched to for the SCs seem to have a regulator protruding out the back instead of the plate which mine has.

Since I've got everyone's attention, ifI can find a way to get the housing machined down, how do I connect this bad boy. I have the /6 schematics, but they don't list what terminals the cables go to. I found the thread on /6 alt. wiring, but without my original alt. it isn't that helpful.



The fat black wire goes to the other terminal, which if I remember correctly is also B+? The black wire in the spade connector I was going to wire to DF, the brown to ground, but I can't tell where the red is going in that picture, D-?

Thanks,

Adam

adam,

here is my internal vr alt. the alt gurus on pp don't recomend internal VRs especially on track cars because of heat and vr failure.

give me a sec on the connections. i only had wires on the 2 connectors, the stock external vr plug was taped off.

this is on a '67 engine.

on the D + post was the fat black wire from the starter along with 2 other wires, (they were together in the factory wire harness.

on the B+ post was one thin wire, maybe brown, (i'm as color blind as they come).

there was nothing on the D- post.

some of the guys on pp had to modify the air guide to fit newer alts with an internal vr.

hope this helps.