772 fans and unstamped fans

[67 kemie ss]

According to what I have read, there were two types of fans produced in 69 - the 772 stamped fan and the unstamped variety.  According to Jerry's 69Z book, the unstamped was far more common, while Kurt's CRG report states:

•There were two versions of an 'unstamped' fan made by Hayes-Albion. 3947838 was the earlier 2" pitch version and 3956684 was the later 2.25" pitch version.

I interpret these comments to mean that the unstamped fan was available throughout the 69 production year such that a 69Z could have had either - and would most likely have an unstamped fan.  Is this correct?  The reason I ask is that I hear again and again from restorers (and HBC included) that the unstamped fan was an 'early' fan and that the dated 772 was used almost exclusively later in the production year.

OK, to be even more specific, would a 5C car have an unstamped 2.25" pitch fan?! 

Thanks!

[z28z11]

My 01C X77 original is unstamped, while my 03D Z11 original is a 772. I thought I read a long time back that the BB cars usually came with a 772, but I'll have to go read up on that from Jerry's Definitive book before casting that statement in stone (I have an unstamped fan for my 12A L78).

Regards,
Steve

[z28z11]

The following is an even better answer from the Archives:

In 1969, the clutched fan changed to a seven-blade design (still 18 inches in diameter) with aluminum fan blades. Cars with AC or K02 received the same fans as the 1969 Z28 and L78/COPO cars. There were two manufacturers of this fan and a mid-year fan pitch change (2 to 2.25"), yielding four variants of this fan.


•The 3937779 fan had a 2" pitch and was made by Schwitzer. It was used early in the 69 production year (until approximately November of 68) and has the part number and month / year stamped on the fan blades.
•The 3947772 fan replaced the 779 fan and had a 2.25" pitch. It was produced by Schwitzer and was used during the remainder of the production year (and through the early 70's) and has the part number and month / year stamped on the fan blades.
•There were two versions of an 'unstamped' fan made by Hayes-Albion. 3947838 was the earlier 2" pitch version and 3956684 was the later 2.25" pitch version. The fans are normally stamped H and FRONT, but no part numbers or dates are stamped on the fans. They are similar to the 772 and 779 fans but with minor design differences (specifically: the design of the center section and details of fan blade rivet attachment).
From what has been observed on original cars, the 3947772 fan and the unstamped fan were used interchangeably and with approximately equal usage. As noted above, the 3937779 fan was only used on early 69 cars.

I guess my unstamped fan for the BB is likely O.K. - now I've got to go dig it out and determine if it's a Hayes or a Switzer, and the pitch.

[KurtS]

That's directly from http://www.camaros.org/coolingsystems.shtml#fan

Not sure what to add. That pretty much tells it all.

[69Z28-RS]

Steve,

The way I read that section on 1969 7-blade fans, ALL of the switzer supplied fans have the PN/date stamped on the blades, and NONE of the hayes-albion fans have the stamped PN, so the existence of the PN stamp establishes which company supplied the fan, and this is true for either the early pitch or later pitch fans from either company.   My original fan is the 772 fan (stamped and dated) which should then be a switzer.  A year or two ago I bought an unstamped unit at Carlisle which should be an Hayes-Albion.   I should do a comparison of the two to see/notate the design differences.   The most interesting aspect of that discussion, which taught me my 'new fact for the day' was the change in pitch mid-year.  Obviously the earlier fans of either company would load the engine less (2" pitch) AND provide a bit less air thru the radiator (less cooling), so they apparently believed they had 'cooling issues' and redesigned the fan pitch for more air (to cool more), but also more HP loss.   

Note: Kinda makes me think the earlier '69 Z28's might have been a bit faster than later ones given the changes thru the year (fan pitch, additional exhaust restriction on later cars with resonators, etc)...   Was there a period of time between when Z28's had the earlier fan pitch, but transverse muffler (w/o resonators)??    Those cars should have been a bit faster right out of the factory..

[BULLITT65]

Gary I am not sure how measurable a difference it would be. You could have 2 cars made the same week and one could have been faster than the other. I don't know if you have heard of the phrase " factory freaks". 99% of the cars are going to run pretty similar, but very so often a cars timing may be slightly off, carb may be adjusted just different enough as well, to ultimately produce a quicker/faster car than most others. I have seen this with brand new identical new cars ( LS camaros, Mustangs). When you also factor in the tolerances of how hard a clutch will grab, and other small items, I would think a fan degree change would be an even harder thing to determine HP wise.

We already know the chambered was more restrictive, but I do think it would be interesting to see of the stock Camaro exhaust systems offered during the year how they would stack up HP wise.  You would have to interchange them on the same car though to really get an accurate reading. I am counting on you to purchase all three systems and post your results on the DYNO....

[69Z28-RS]

Of course I know what you are referring to.   I wasn't saying to take 'any camaro' and make those tiny changes to make it the fastest one of all..   I'm only saying that there are measureable difference in HP losses with each of those changes, and racers adage 'every little bit helps'.    Taking ALL of the cars produced during a several month period, some will be faster and some slower.. just as you say.   But if you take it to the extreme that you made it sound, no one would ever make any changes to their car because it was either 'fast' .. or 'slow' right out of the factory.. 

PS.  *Everyone* always believes theirs was one of the fast ones.. 

Gary

[HawkX66]

I guess my unstamped fan for the BB is likely O.K. - now I've got to go dig it out and determine if it's a Hayes or a Switzer, and the pitch.

It definitely could be. This one is original to my 69 SS396 (no stamps on the blades):

[69Z28-RS]

when I first examined my original Z28 fan, I couldn't see any stampings on the blades, but after lots of cleaning (using a little fine steel wool along the edge, I did find the '772 stampings and date'...  If the fans have been painted (and repainted maybe?), you may not think numbers are there..  they are very lightly stamped...

[z28z11]

I guess my unstamped fan for the BB is likely O.K. - now I've got to go dig it out and determine if it's a Hayes or a Switzer, and the pitch.

It definitely could be. This one is original to my 69 SS396 (no stamps on the blades):

Definitely a Switzer fan clutch - looks identical to the '68 Z clutch, except I'm unsure about the bolt circle. Surprised it's not an Eaton - early '69 build date ?

Regards,
Steve

[bergy]

Z-28 is longer shaft and BB is shorter shaft - right?  These are all dated in the Jan-June '69 time frame.

[69Z28-RS]

Sarge,

Pictured below is my original fan; the areas along the blade edge which has the paint partially removed is where the stamped numbers are.  All the blades are stamped identically in the same location on each.  Note:  Mine is a late car (fan dated H69) and is a 2.5" pitch.

I notice the rivets are totally different between your fan and mine.   Different manufacturers??

[VINCE Z28]

Also your arms are more square then his.

[HawkX66]

I looked pretty close at mine and I couldn't find any numbers other than the date that I posted. Kurt and I had talked about it quite a while back and his feelings were it was original and he wasn't surprised it didn't have the stampings. Gary, your car and mine are pretty close in dates. Mine rolled off the line on August 22, 1969. There's no evidence that the fan was repainted at any point and I know positively it hasn't been painted since 1982.
I'll take another look when I get home tonight, but I seriously doubt I'm going to find anything.

[69Z28-RS]

Sarge,

Per the CRG info, and your photo, you have a Hayes-Albion mfg fan, and those aren't stamped...... explains why mine and yours are so different.
When you get a chance, lay it down flat and measure the height of the highest part of a blade....  since it's a late car, it should be 2.25" inches..