fan clutch 3916141 hub dimension

[John R.]

I have a 3916141 NOS fan clutch. The hub that mounts to the water pump is 2 1/2 inches wide. It will not fit through a 2 3/8 inch C2 fan opening. All the attributes of the fan clutch indicate it is the correct design Eaton BB fan clutch. What application is it for with the 2 1/2 inch hub? What fans have an opening that are 2 1/2 inches or wider opening? C3??

Face of clutch has the following ink stamps: 0X3-87700 and D2J.

Thanks in advance for helping me figure this out.

[John R.]

Re: fan clutch 3916141 hub dimension

I guess it is better to define the hub as the mounting flange. It is in a GM box with 3916141 part number stamped on it, and it has a 2 1/2" mounting flange. Looks line the distance from the fan mounting surface to the flange mounting surface is 1 3/8" or so. Here is a photo of the face.

[Harry S.]

Re: fan clutch 3916141 hub dimension

John, just measured a Schwitzer and an Eaton. The Schwitzer was 2.30" and the Eaton was 2.28". I've used them both on my 63.

Sorry, can't help with the 2.50 Eaton.

[Joe L.]

Re: fan clutch 3916141 hub dimension

I guess it is better to define the hub as the mounting flange. It is in a GM box with 3916141 part number stamped on it, and it has a 2 1/2" mounting flange. Looks line the distance from the fan mounting surface to the flange mounting surface is 1 3/8" or so. Here is a photo of the face.

John------


This is either a bogus reproduction or it's been mis-labeled as a GM #3916141. I suspect the former.

The front of the piece does appear like the early configuration of the 3916141. However, you don't picture the REAR which is what I really need to see. In any event, the 3916141 should have a hub OD as Harry describes. In addition, it should have a 4 hole hub mounting pattern with a 1-3/4" bolt circle and a 5/8" pilot hole.

In 1971 Corvettes went to a fan clutch with a 2-1/8" bolt circle and a larger OD hub (probably the one you have). These cannot be used with any pre-1971 fan blade assembly because the hub will not fit through the center hole. The 1971+ hubs also have a 3/4" pilot hole.

[John R.]

Re: fan clutch 3916141 hub dimension

Harry and Joe, thanks for the feedback. Here is a photo of the mounting flange with a tape measure. I also noticed it does not have the studs.

[Joe L.]

Re: fan clutch 3916141 hub dimension

Harry and Joe, thanks for the feedback. Here is a photo of the mounting flange with a tape measure. I also noticed it does not have the studs.

John------


The bolt pattern and pilot orifice look correct for pre-1971. However, the hub is too large OD and won't work with pre-1971 fan blade assemblies. I wonder how many of these "reproductions" that some supplier has? All of them are, essentially, useless.

[John R.]

Re: fan clutch 3916141 hub dimension

Joe, that's interesting. Just curious, what are you observing that makes you think this is a reproduction? Have attached a few more detailed photos. There are 3 paint colors on the clutch. Orange dash on the hub perimeter and yellow and blue on the fins. Would a reproduction go to that much detail? What does the paint mean? Also included a photo of the box. Looks like a 1984. Does that somehow correlate with the date on the clutch D2J??

Original hubs did not have a beveled hub edge, did they? The edge of this hub is beveled. I wonder if that bevel was supposed to have been milled off? I think that would put it at the actual correct dimension. Or perhaps this is just a clutch that found its way into a 3916141 box but is not a 3916141 clutch.

[John R.]

Re: fan clutch 3916141 hub dimension

Adding the 4th photo...Orange paint dab on hub.

[Joe L.]

Re: fan clutch 3916141 hub dimension

Joe, that's interesting. Just curious, what are you observing that makes you think this is a reproduction? Have attached a few more detailed photos. There are 3 paint colors on the clutch. Orange dash on the hub perimeter and yellow and blue on the fins. Would a reproduction go to that much detail? What does the paint mean? Also included a photo of the box. Looks like a 1984. Does that somehow correlate with the date on the clutch D2J??

Original hubs did not have a beveled hub edge, did they? The edge of this hub is beveled. I wonder if that bevel was supposed to have been milled off? I think that would put it at the actual correct dimension. Or perhaps this is just a clutch that found its way into a 3916141 box but is not a 3916141 clutch.

John------

There are several things that make me believe this is not an original GM #3916141. First of all, the configuration on the front of this fan clutch is the very early style as used and available back in the 60's and 70's. Note the rectangular silicone fluid reservoirs. I don't think this style was even being produced as late as 1984. By that time I believe these reservoirs had been changed to the "trapazoidal" shape. However, I think the early style face is available in reproduction.

Another discrepancy is the ink-stamped coding. I've never seen a coding like that pictured. It looks odd to me. In addition, the 3916141 usually has a "CK" ink-stamped code on the face.

Usually, GM #3916141 hubs did not have the bevel but I could not say that none ever did. In any event, I HIGHLY doubt that the bevel was machined there as a prelude to machining it off and reducing the OD of the hub.

Usually, the GM #3916141 was supplied with studs for fan attachment. However, once again, I do not know that all were. These things were available in SERVICE for a very long time.

This fan clutch does have the inspection marks that one would expect on a GM #3916141.

It's of course possible that this piece is an original GM piece but an "off-spec" example. If so and it had been recently purchased from a GM dealer, one could obtain a replacement or refund under terms of the GM parts warranty. However, that would be moot at this point.

Whether it's a reproduction or an "off-spec" GM piece is kind of moot, too. Either way, it's unusable as it is. I would not recommend attempting to machine the OD of the hub as that could affect the balance.

Was this clutch is a SEALED box when you got it?

[John R.]

Re: fan clutch 3916141 hub dimension

Joe, box was open.

[John R.]

Re: fan clutch 3916141 hub dimension

Joe, the conclusion is this is not a 3916141 clutch. I assume it is possible it may be a for other GM applications. Saw this from a post you made back in 2011.

Some later 60's-early 70's passenger cars use hub mounting pattern the same as 1960-70 Corvette BUT fan clutch-to-hub mounting pattern same as 1971-82 Corvette. No Corvette ever used this combination, though.

[Joe L.]

Re: fan clutch 3916141 hub dimension

Joe, box was open.

John-------


I have another thought here. I believe there were some pre-1971 Chevrolet applications (maybe full size Chevrolets) which used a fan blade assembly with a 3-1/4" bolt circle (with a 2-5/8" center hole) but with the pre-1971, 1-3/4" bolt circle hub and 5/8" pilot. If so, such an application would have used a fan clutch configured as you have. So, this could be an original GM fan clutch but of a different part number than 3916141 that somehow found it's way into a 3916141 box.

By the way, if I'm right about this, it would not do you any good to reduce the OD of the hub because the bolt circle of the fan blade attachment of the clutch will not match your fan blade assembly (i.e. it'll be a 3-1/4" bolt circle versus the 3" bolt circle of your fan).

[John R.]

Re: fan clutch 3916141 hub dimension

Joe, you hit the nail on the head! Bolt circle is 3 1/4". I guess it is original, just not in the correct box. I do see that certain 1968 Camaro's used the 3.25 bolt circle and should still have the small hub and short water pump. I wonder if the stamping on the face would tell us anything regarding the part number?

[Joe L.]

Re: fan clutch 3916141 hub dimension

Joe, you hit the nail on the head! Bolt circle is 3 1/4". I guess it is original, just not in the correct box. I do see that certain 1968 Camaro's used the 3.25 bolt circle and should still have the small hub and short water pump. I wonder if the stamping on the face would tell us anything regarding the part number?

John------


I can't make out any sort of GM part number or derivative thereof for any fan clutch used during that period. My GUESS would be that this is a GM #3927103.

[John R.]

Re: fan clutch 3916141 hub dimension

Joe, thank you for helping me with this clutch identification.