Here are photo's of 3 one pice pulley/fans for the 66 alternators. Two of them have the correct # 3843342AJ stamped on them along with the single digits 2 and 12 stamped on the back side . You will notice the spot welding the the pulley to the blade is a little different.

The 3rd pulley came off a July 65 dated alternator, it does not have the number stamped on the front face; but is exactly like both of the first two with the only difference being the spot welding on one but not the other, and it has a 6 stamped on the back side. This alternator still had the correct non-spit type lock washer and correct nut and appear to have never been disassembled.

Would all of these be original? Or just the two with the part# stamped on the front face? Did infact some pulleys not have the # stamped on the face.

I have also run into this situation regarding the stamping of the # on water pump pulleys.

No opinions yet? Isn't anyone going to ask me what happend to the one with the busted blade?

Isn't anyone going to ask me what happend to the one with the busted blade?

:noway: :D

Well just as a precaustion to other, evidently I didn't have my belt on tight, or I installed it with a twist. After feeling something hit my face while fiddling with the throttle and hearing a click sound I shut the engine off. The belt was twisted on the alternator pulley and I guess it forced the fan to scrape the face of the alternator. Fortunately I had glasses on.

Any opinion as to whether original pulleys must have a # stamped on them?

As to a stamp or no stamp, it is not uncommon for a given pulley to not have a # stamped on it in early production, and for the # to get added in later production. Examples are the deep groove water pump pulley and d.g. alternator pulley on a Z16. They are not stamped. But the 67 Chevelle L78 pulleys (which have the exact same part nos.), and NOS replacement pulleys, are stamped.

So, if you assume no stamp means earlier, and having a stamp means later, then I'm going to throw out a complete guess here on your 3 pulleys (then check my stash of old alternators this weekend to see if I'm right) --

Based on the July date on your 65 alternator, the unstamped one with a 6 on the back was probably made in June of 1965. The stamped one that has the same spot-weld design as the 6/65 fan is probably the second oldest, and the 2 on the back of it probably means February (66 or 67 or ... ). Then the third one is probably newer than the other two since it has a completely different spot weld design which looks like what later alternators used, and the 12 on the back of it probably means Dec (66 or 67 or ... ). Again, this is just a semi-edumucated guess :thumbsup:.

Thanks, they changed the pulley in 67 sometime to # 3909815. Very similar to the 3843342 pulley. The 3909815 from my information was then used as a service replacement. for the 3843342 pulley.

The spot welding on the pulley with the 12, is the same type as a 3909815 pulley that I just looked at.

So my guess would be June of 65 (this pulley came on an alternator dated 5F or June of 65), feb of 66, and dec of 66 as you suggested. I also have an older pulley with a little different design (all the fins are the same size and came on a 64 dated alternator), that I think was used in 63 or 64 and it also has the circular spot welding and no number stamp. Thanks.

FWIW I have a 1100693 alternator with a date code of 6M2 on my 67 Chevelle and it has the 3909815 alternator pulley with fan on it. That is also the pulley that is listed in the AIM, so I do not understand how that could be listed as a service replacement :confused:.

FWIW I have a 1100693 alternator with a date code of 6M2 on my 67 Chevelle and it has the 3909815 alternator pulley with fan on it. That is also the pulley that is listed in the AIM, so I do not understand how that could be listed as a service replacement :confused:.

They stopped making and selling the 66 part no. pulley/fan for service replacement usage, and replaced it with the 67 pulley/fan. My GM superceded #'s book says that occured in July 1967. So if you broke your 1966 pulley/fan (like James just did) after that date and went into your dealer to buy a new one, you'd get a 3909815 instead of the original 66 part #.

Jeff