1972 Mystery Fan

[John H.]

I know it may never be known for sure, but maybe your comments may
add a few peices to the puzzle. I am the original owner of 1972 coupe
built in February 1972 and delivered to dealership in February.

I then purchased the car new in May 1972, about 3 months later.
AT the time this dealership had about 25 corvettes for sale, near Navy
Pilot base, Pensacola Florida. Gas lines, crunch.
The interesting item is the FAN has a March build date. I have a diary
of every repair, any work done on my car since first oil change.
I knew I would keep this car for ever...Following Facts Very Interesting.

1. March fan, but car has Feburary build date ?
2. Car was at dealership about 3 months.
3. In the glove box I found 2 pages of GM installation procedures
for installing a OVERFLOW BOTTLE and tubing routing.
This installation instruction sheet was for a 1971 truck model
as the example.

I have lost judging points every time for the March dated fan, however I
will never change that fan.

4. It is also very strange that my HOOD ONLY, appears to have small
bubble marks on it's surface. These bubbles started to appear
about 5 years ago. Possibly due to long term heat build up ?

What my question to readers is WHAT DO YOU THINK HAPPENED ?

[Terry M.]

Re: 1972 Mystery Fan

Fan: Stick to your guns. Some day someone will find the answer, and if not you know it is the one that was on the car when you bought it. The judges are just doing their job when they deduct for it, and they should. THAT is the system.

Glove box stuff -- who knows. Someone probably spent a lot of time looking for those instructions while the truck sat in the bay.

4) I would wager you have C60, air conditioning. It is very common for the A6 compressor to sling oil from the front seal. If this oil lands on the underside of the hood it will eventually soak through the fiberglass and push its way up under the paint on the hood resulting in bubbles. I just saw an original paint 1972 at the London Ontario Regional with this issue -- that car is Black. I have seen others, and usually the paint blisters are more prominent in line with the front of the compressor, but sometimes they are all over the hood. You will never be able to get rid of them if they are from the HVAC oil. Even stripping and refinishing will not, in the long run, be effective. Learn to live with them.

[Loren L.]

Re: 1972 Mystery Fan

Check date on H2O pump, fan clutch, scars on the shroud. I would suspect that while the car was waiting on you, either the pump or th fan clutch had a failure that chewed up the fan beyond acceptable appearance and it was replaced.

[Don L.]

Re: 1972 Mystery Fan

Check date on H2O pump, fan clutch, scars on the shroud. I would suspect that while the car was waiting on you, either the pump or th fan clutch had a failure that chewed up the fan beyond acceptable appearance and it was replaced.

...or perhaps the original fan was called on as a donor for service replacement on another car before you bought it? I've benefited from "lot parts inventory" in the past, so it does happen.

[John H.]

Re: 1972 Mystery Fan

Guys you have all helped me to better understand these issues.
I didn't know about the oil/bubble effect before this comment, very
interesting, a BIG thanks.
Also I am going to inspect the fan shroud as suggested, another good
tip.
About the overflow paperwork. These pages were actually in the
glove box....Very strange.....
When I first submitted this post I thought I might be Stupid for asking
for comments, but you NCRS guys came thru again...Super Job to all.

Another neat part of the Corvette original purchase is that I had spoken
to salesman, long distance call and he said when I fly into Pensacola
from New Orleans he said "call me from airport next week and he would
pick me up at the airport".
That next Saturday he drove up in a beautiful red corvette for the drive
back to the dealership. We discussed the deal, they where hard pressed
to sell corvettes due to the gas shortage back in 1972.
Sticker price was about $6500, he took off $1100, sold it for $5400...

By the way that red corvette ride from the airport, that's the car I own
today....Save The Wave....Big John

[John H.]

Re: 1972 Mystery Fan

To Terry, Don, Loren......I checked the NCRS Technical Information &
Judging Guide, 1970-72 Fourth Edition page 84 Fan Clutch.
My car is a a/c base 350 1972 4sp.
"Clutches had a date code stamped on the EDGE SURFACE of the flange
that bolts to the water pump pulley." I.E. a March 10,1970 built car the
fan clutch is coded 2-16-70 SC for February 16,1970.
My question is THIS FLANG AREA appears to have a DIAMETER of about
3 INCHES AND ABOUT 3/8 inches in thickness. IS this the Flange Area
WHERE date should be ? Since this area is a ROTATING assembly I would
need to bump the engine slightly until date might appear.
Does this sound correct ? Thanks Big John

[Terry M.]

Re: 1972 Mystery Fan

Yes John, that is the area for the Schweitzer Corporation (SC) clutch -- the one with the flat bar in front. That is the one I would expect your car to have. A mirror might prevent the need to "bump" the engine.

You might have an Eaton clutch -- with a coil in the front. I believe the Eaton clutch does not have a date code visible when installed (and maybe they do not have one at all). Others on here will know more about the Eaton clutches than I do.

[David L.]

Re: 1972 Mystery Fan

You might have an Eaton clutch -- with a coil in the front. I believe the Eaton clutch does not have a date code visible when installed (and maybe they do not have one at all). Others on here will know more about the Eaton clutches than I do.

Terry,

The Eaton fan-clutches (coil type) were stamped on the face with an ink stamp date code (about 1 /4" size digits) which faded with age so after 40+/- years it may be very difficult to see.
Examples from a 1970 Z28:
"EATON CV" and "A20A" (Jan. 20, 1970)
"EATON CV" and "D9A" (April 9, 1970).
The "CV" = GM # 3946804

1971 Monte Carlo fan-clutch:
"EATON AG" and "E4B" (May 4, 1971)
The "AG" = GM # 4950822

I also have a 1970 Pontiac coil type fan-clutch made by Delco Prod. Div. G.M.C. of Dayton, Ohio, with an "PC" ink stamp on the front face and "4949706" and "034 70" (34th day of 1970) stamped on the back side of the flange. The clutch must be removed to see the stamped part number and date code.

Dave

[Terry M.]

Re: 1972 Mystery Fan

Thanks Dave, I had forgotten about the AC Delco made fan clutches -- but we almost never see them on Corvettes, however, some years the AIM shows three optional part numbers for the fan clutch, so it is a possibility. Jack Humphrey wrote a story for The Corvette Restorer about that once upon a time, and he will lash me with a wet noodle for forgetting.

Since we have a hard time judging the front of the fan clutch as it is installed, and we see so few Eatons, our depth of knowledge is well ... lacking.

[Kurt G.]

Re: 1972 Mystery Fan

John, I don't know what to tell you about the fan, but as for the paint, my September 13, 1971 built car has the same hood "bubbles." Contrary to the comments about the A/C compressor slinging oil, which they do, the condition you have is called "solvent pop." It is caused by an uneven disipation of the solvents in the paint. The most probable cause is the use of a wax on the hood before the paint had a chance to really "cure", which I've been told took over 6 months even with the baking of the paint like they did. The "bubbles" look a lot like tree sap on the hood. The waxing of the hood in particular trapped the solvents, which when the engine heated the hood up, tried to evaporate and couldn't. I don't like mine, but I'm not about to do anything about my otherwise 5 foot all original unrestored car.

[Scott K.]

Re: 1972 Mystery Fan

I've got the hood bubbles above my compressor too.
It's definitely oil from the ac compressor wicking it's way through the glass.
Just live with it.

"Corvettes are like diamonds, the best ones have small imperfections that help you identify their originality."

Scott.