Alternator 902 903 904
 

Hi group.from what I seen hear and read Im confused a little on alternators for 1970. They are all open face and finned I believe. But seen black.fans zinc fans ,black pullies,zinc pullies,and gold. Then spokes. Are they 6 spoke, 5 spoke or both.i was told 5 only but seen 6 and then was also told 6 and 5 spoke. I realize it's a small detail but still curious. School me please. My car assembled In March of 70

The earlier open face alternators for 1969-70, including the 902, 903, and 904 were 6 spoke. For the 1971 model year including the 927 and 928, they changed to five thicker spokes.

Also, from what I have seen, the fans and pulleys were both silver cadmium.

902903904
 

Thanks

As said, and I agree 1970 are 6 spoke. However, and was JUST DISCUSSED in another thread in this very forum, the Pulley is Gold Cad and fan is Galvanized ( which I have been doing in silver cad paint as The Galvanized paint is weird, and seems a 1 use deal per can. )
So, PULLEY WAS GOLD CAD ( I have Originals to prove this)
FAN WAS GALVANIZED
Are we done yet?
Want your pulley done Correctly? This involves bead blasting, treating, Silver zinc plated, and then DiChromate coating.

lets do some pics
https://forums.maxperformanceinc.com...4&d=1648248456
https://forums.maxperformanceinc.com...5&d=1648248465

Alternator
 

Wow that's a lot of detail. Is the pullies all the same because I got about 10 alternators at home . Like to see pics of correct fan too

Pullies I have pulled 70 and 71 and 72 were ALL Gold "cad" .
I have a correct fan, will have to look again, the Galvanize gets gray and dull and makes it hard to see the flakes on the coating.
They didnt last a year in appearance in normal use.

https://forums.maxperformanceinc.com...d.php?t=715554

My '903 was pictured here and was a 5 spoke. Can't tell what the plating was...

I am almost certain that some of the very early/first run 1970 alternators 902/903 had the 5 spoke front and the changed came pretty shortly into the 1970 run...
TellyS.....didn't we discuss this before? I think there were known examples out there...

I think i had that backwards.....Maybe strike what i said....I may be thinking that the 69 had 6 spoke (correct) and that some of the later built 69's went to 5 spoke...BEFORE the eventual release of the 1970 style....

OK Telly is texting me on the side probably laughing at the confusion i am causing...He claims 6 spoke up until sometime in May 1970.....

And you want to be my latex salesman!


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Jeff!!! WTH....Cant get away from those references after 25+ years..
SERENITY NOW!

formulabruce,
its ignacio and like to know where i can buy a cad pulley for my custom built 904 alternator and possible zinc fan with1 wide blade?

this made me chuckle.

ok, I saw this discussion before, but today I was prompted to look;
My '902 alternator is a six spoke, and is dated January 27, 1970.
I also have an unstamped front housing that is a six spoke design.
Now, many don't realize it, but the early (69/70) alternators also have a unique rear case - I swapped my rear case for a later one because the bolt boss for the rear mount is damaged - but I kept it with the front of that alternator that I swapped the rear case for.

I hope you're not losing sleep over this minute detail;
Not once was my correct alternator noticed.

The cad looking coating used today looks different on different metals. On carbs it looks perfect. On a steel pulley, even though its zinc plated first, the gold looks a bit brighter. Ignacio. I am going to do a few pulleys this summer. I will be sure to post some pics and save one for you if you like it. Your alternator has no fan or Pulley?

I unfortunately don't have my original 904 or ever seen 1. Haven't been able to find1 either. I located 2 928, and 3 open face blanks and 1 diamond finned 70 back that's slightly chipped. So I got the idea to have one custom made with a blank and correct rear back cover. I could pay extra to have it professionally stamped and say I have an original but I'm not like that. So I want correct fan and pulley

honestly, my suggestion would be to build an alternator with the common (not 69/70) rear case, and leave it unstamped.

I'd wager that people would notice paint/plating way before stamping, or the rear of the alternator case;
Also, without a 1970 Firebird (suppliment) service manual, or a Master Parts Catalog, I wouldn't know what the correct alternator number is for our cars - the Firebird Red book, and HPP 'numbers crunching' never mentioned the alternator - it wasn't till years after the fact that I realized I had the correct for my car alternator.

904
 

Oh it's small detail I guess. This is what I got so far. The front ooen face isn't an original but a blank. I got 2 like this when done probably sell other core.

I was astonished when I saw what the rear cases were going for - I looked into it with hte idea of replacing my 902's original - but quickly changed my mind.
I bought an unstamped open face front case to basically make a backup or sit in replacement for my '902.

Rear
 

The bavk.finnwd diamond did cost , and it is a diamond finned. Do you know of the 69 version that has a mounting bolt at the 6 pack instead of 4 oclock.still works if you actually rotate the rear 90 degrees counter clock wise

The rear case needs to be clocked with the plug at 9 oclock (viewing from the back) to be in the correct place for the wiring harness.

Also, pulled the fan and pulley off my unrestored 902 (April date code) to check plating. I can see what looks like a lighter gold plating on the back of the pulley. The fan is cad. Pics below but hard to get the lighting to see the gold on the pulley. The last pic is the fan and pulley from a later 60s 10dn alt. Clearly cad on both. Same fan style as 902.

interesting so the pully and fan are cad? i read pully only lol this ias confusion stuff. also read all zinc too! can anyone tell me correct pulley detain for a 904 with power steering and ac? i dont know the diameter or v groove depth.
thanks

I was pointing out that the late 60s pulleys looks silver cad but the pulley off my 902 looks possibly gold cad or zinc. The fans both look to be silver cad.

Fan and pulley
 

What's the diameter and v groove of pulley? Is there any special.offset?

The pulley on my 902 is 2-3/4" in diameter.

thanks alot now i need to find a cad pullkey or get one plated. Thanks

Just to jump into the mix here since I’m in the hunt for a 902 alternator myself now. Had a great phone conversation with RamAirNacho earlier today. For a car with an 06C build date, what would be a reasonable alternator build date. I read on a Camaro forum that they use anything from 2-weeks before the build date to a couple of months back. Was Pontiac any tighter on these dates than the Chevy clowns? Lol. Just kidding.


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