71 BB Fan Clutch Restoration/Cleaning

[John L.]

I tried the archives...OK I'm better cleaning than searching.
My original clutch is in good shape just extreamly dirty and in need of a good cleaning. I want to be careful and not use something that could cause discolorment to the casting. Also in the 70-72 TIM&JG it says the back side is painted (Dull Aluminum Color) W/ a dot of yellow on the mounting flange. I assume the mounting flange and shaft are also painted?
Appreciate any help on cleaning hints and verification of (Dull Aluminum Color) on the shaft and flange.
Thanks in advance for your help.
John Liner

[Kenneth T.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Hi John,

I have a '71 LS5. My fan clutch is has a natural aluminum finish not unlike your alternator would look. the front looks to be lightly zinc plated not as yellow as your headlight door actuators but not grey or aluminum color, also there are numbers in black painted on it. The shaft is not painted. I hope this helps.

Ken

[John L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Kenneth also mine is not painted, wasn't sure why the TIM&JG calls for it to be painted. My shaft and mounting flange doesn't look to have ever been painted, also the aluminum clutch doesn't appear to have been painted in the past. I would like to clean it back to a shiney look, repaint the fan blades and make everything appear new. What I don't want to do is to use too harsh a cleaner on the aluminum and discolor it or worse affect the seal on the shaft. Thanks for the reply.
John

[Joe L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

I tried the archives...OK I'm better cleaning than searching.
My original clutch is in good shape just extreamly dirty and in need of a good cleaning. I want to be careful and not use something that could cause discolorment to the casting. Also in the 70-72 TIM&JG it says the back side is painted (Dull Aluminum Color) W/ a dot of yellow on the mounting flange. I assume the mounting flange and shaft are also painted?
Appreciate any help on cleaning hints and verification of (Dull Aluminum Color) on the shaft and flange.
Thanks in advance for your help.
John Liner

John-----


All 1971 Corvettes used fan clutch GM #3991426. This is a Sweitzer-manufactured clutch with a "bi-metallic" plate type thermostat. These clutches usually have what appears to be dull aluminum paint on the shaft and hub. They also have a stamping on the perimeter of the hub which, among other things, contains the characters "SC" (for Sweitzer Clutch).

By the way, Eaton-manufactured clutches, which use the "coil spring" thermostat, do not have the painted shaft and hub. However, I don't think that any of these were originally used for any 1971.

[John L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Thanks Joe,
I do have the correct clutch, mine looks to have never been cleaned and it looks like it could stand a good cleaning and freshing up. The hub and shaft is rusty and will need to be bead blasted or wire brushed off before I can paint them. Would you happen to have a good photo showing the dot of yellow on the hub? Also could you reccomend a cleaner to clean the aluminum clutch, it has dirt, grease and a little corrosion on it. The fan blades need stripped/wire brushed and painted before reassembly.
As always thank you for all the valuable information.
John

[Joe L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Thanks Joe,
I do have the correct clutch, mine looks to have never been cleaned and it looks like it could stand a good cleaning and freshing up. The hub and shaft is rusty and will need to be bead blasted or wire brushed off before I can paint them. Would you happen to have a good photo showing the dot of yellow on the hub? Also could you reccomend a cleaner to clean the aluminum clutch, it has dirt, grease and a little corrosion on it. The fan blades need stripped/wire brushed and painted before reassembly.
As always thank you for all the valuable information.
John

John-----


I don't have a photos showing the yellow dot on the hub.

To clean the clutch, I would recommend as I do for most things: use the LEAST aggressive cleaning method first and progress from there only as necessary. I'd use hot water and soap as the first method. This shouldn't harm anything and may be all you need. Progress from there to something like 409 cleaner if you need to. Neither of these will remove corrosion, of course. For that, I'd use a BRASS wire wheel on a drill and treat the spots evidencing corrosion.

[Patrick H.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Thanks Joe,
I do have the correct clutch, mine looks to have never been cleaned and it looks like it could stand a good cleaning and freshing up. The hub and shaft is rusty and will need to be bead blasted or wire brushed off before I can paint them. Would you happen to have a good photo showing the dot of yellow on the hub? Also could you reccomend a cleaner to clean the aluminum clutch, it has dirt, grease and a little corrosion on it. The fan blades need stripped/wire brushed and painted before reassembly.
As always thank you for all the valuable information.
John

I recently cleaned one up for a 64.

I immersed only the hub and shaft in Ridrust (http://www.safestrustremover.com) and it cleaned them up nicely. I then used blue masking tape to cover original factory green ID paint between several of the fins, and also covered up the bimetallic strip on the face. I then used my benchtop blaster with small glass beads to gently clean up the clutch. It looked great!

Patrick

[Jack H.]

Re: 71 BB Fan Clutch Restoration/Cleaning

On the issue of the color code marks, some research needs to be done before assuming these are correct for your '71 car...

If I remember correctly, this was a running change item and you need to lay the '71 AIM next to a copy of the '72 AIM book. Here's a copy of the '71 AIM where the fan clutch for the BB is called out (3991426). Note it changed PN at the beginning of the model year from the 3937771 clutch used in 1970 (different hub geometries for the different model years in addition to mating hub changes on the water pump).

View C shows the pump came with a cardboard seal that was removed and discarded prior to the fan and fan clutch being installed on the water pump. You can see there are NO notes on the drawing regarding any color codes!

Now, still going from memory, if you compare this to the equivalent page from the 1972 AIM book, all of a sudden there ARE call outs for aligning the fan clutch to the water pump during assy based on each having distinct color codes (one yellow, the other green?) to achieve the best overall alignment/balance.

I also remember the '72 AIM drawing documenting the AIM date associated with these parts having color coded alignment marks on them. This makes me believe this was minor a running change associated with drawing release for the upcoming 1972 MY release of Corvette.

So, despite what you've read/heard about the fan clutch having a daub of color (it would have been rather sloppily applied to the outer edge of the drive hub), methinks this is an early vs. late car running change issue...

[John L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Jack you are correct, I will check futher into this. After I get everything cleaned up I may or may not find any traces of paint, my car is a mid to late 71.
Patrick, thank you for the tip on the rust removal solution, I will order some to try. Joe you are correct I will start with the most mild solution to clean, good idea on the brass wire wheel to remove the corrosion.
Thank you to all who responded!

[Patrick H.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Jack you are correct, I will check futher into this. After I get everything cleaned up I may or may not find any traces of paint, my car is a mid to late 71.
Patrick, thank you for the tip on the rust removal solution, I will order some to try. Joe you are correct I will start with the most mild solution to clean, good idea on the brass wire wheel to remove the corrosion.
Thank you to all who responded!

John,

How late is your car?
My 19518 definitely had the paint on it.

Patrick

[Kevin G.]

Re: 71 BB Fan Clutch Restoration/Cleaning

My 71 bb does have the yellow paint mark, and I have been trying to get a picture up for you. However, with the fan and clutch assembly on the car it's a bit tight for my large camera. I will give it another try for you. Also, vin # 8555, Feb 2nd build date. Picture to come!
Kevin

[John L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Thank You Kevin, that would be great. There could be some paint on mine, I have to do a lot of cleaning, maybe it's there and I can't see it.
If not a photo showing where it should be would be very helpful.
Thanks

[John L.]

Re: 71 BB Fan Clutch Restoration/Cleaning

Patrick,
Vin 17,344
Date 5-71
Thanks...John

[Patrick H.]

Re: 71 BB Fan Clutch Restoration/Cleaning

It would not be unusual for the yellow mark to wear off.

I've got a great mark on my car, but as usual I was by it yesterday and won't be back until this weekend.

Patrick

[Kevin G.]

Re: 71 BB Fan Clutch Restoration/Cleaning

John,
Hope this helps, the small yellow paint is not as visible as the green dash on the pulley. Just above the nut is a small yellow paint mark and just after the numbers on the edge of rim.

Regards,
Kevin