Best Replacement Fan clutch for a '74 BB w/air?

[Tom M.]

GM I was told no longer services this part, is there a good replacement that I cam get from CarQuest, NAPA, etc? I would like one that works and looks as correct as possible.

Thanks,
Tom McCabe

[Joe L.]

Re: Best Replacement Fan clutch for a '74 BB w/air

Tom-----

The original fan clutch used for your car was GM #343721. This was an Eaton-manufactured clutch coded "AX". It was discontinued from SERVICE in October, 1996 and replaced by GM #12529342. This fan clutch was absolutely identical in configuration and performance to the 343721. In my opinion, these 2 fan clutches were ABSOLUTELY, POSITIVELY the best fan clutches EVER used on a Corvette. I love these things so much that I purchased ELEVEN of them over the years and they're "resting comfortably" in the collection [none for sale]. They were never used on a 1969, of course, but they're used on MY 1969, even though other changes had to be made to accomodate the installation. One will be used for my "ZL-1" conversion, too. You can bet on that.

Within the last few years, the GM #12529342 has been discontinued and replaced by GM #88961768. This unit appears to me to be virtually identical to the 12529342. The one difference that I have noted is that the hub has a dual bolt pattern whereas the 343721 and 12529342 did not.

As far as I know, the 88961768 remains available through GM and Delco dealers. That's THE one that you want to use, too. Absolutely. POSITIVELY.

[Gary B.]

Joe: difference between 88961768 & 3916141?

Joe,

What's the difference between the fan clutch GM # 88961768 and GM # 3916141? Is the former for BB and the latter for SB? If so, it would be a rare time that the SB part is much more expensive than the BB part.

Gary

[Craig S.]

Re: Joe: difference between 88961768 & 3916141?

Gary - the clutch Joe is discussion is MUCH more substantial than the midyear clutches (I have an original 74 besides my midyears and can attest to the beefier construction). I know the differences on use include the bolt circle (but Joe mentions the newest version is dual drilled) and the center has a 3/4" hole for the larger water pump shafts. I also expect there are some length differences from the mounting flange to the fan mount area on the clutch as well affecting fore and aft spacing......but I am sure Joe has compared them far more closely than I! Craig

[Gary B.]

Re: Joe: difference between 88961768 & 3916141?

Craig,

I'm hoping Joe can tell us if the BB fan clutch will work on a SB application, since the combination of a beefier design and much lower cost is very appealing.

Gary

[Joe L.]

Re: Joe: difference between 88961768 & 3916141?

Gary----

Actually, the GM #3916141 was a big block fan clutch that later became SERVICE for small blocks, too.

The big FUNCTIONAL difference here, though, is that the 3916141 has the small hub bolt pattern used for 1970 and earlier. It also has the small fan mounting bolt pattern used for 1970 and earlier. So, unless other parts are changed, it will only work for a 1970 and older application.

The GM #88961768 is a fan clutch which replaces earlier clutches originally used for BOTH small block and big block applications. This fan clutch has a dual bolt pattern (and, likely a 3/4"-to-5/8" bushing packaged with it), so from the hub perspective it could likely be used for any Corvette application, pre or post 1971. However, I believe that the fan mounting pattern is the larger, 1971 and later pattern. So, a 1971 and later fan would have to always be used with it.

Actually, I would not recommend that the 88961768 (or, any of it's predecessors) be used with a 1970 or earlier small block application. I don't think that the 5/8" shaft used for all 55-70 Corvette small blocks is stout enough to support long-tem operation with this clutch. It could easily be used, though, if a 1955-70 application were converted to a 1971+ small block waterpump. For big blocks, it wouldn't matter much since all big blocks use a 3/4" waterpump shaft (although 65-70 had a pilot diameter reduced to 5/8").

If the 88961768 is, indeed, like its predecessors (and, I believe that it is), it will really cool. That's really the other functional difference between the 3916141 and the above-referenced. The 3916141 is a bit "weak-kneed" when it comes to cooling whereas the above-referenced is "herculean". I mean, for a fan clutch, these things are THE ONE.

Configuration-wise, the 3916141 and the 88961768 and its predecessors are TOTALLY different. You'd NEVER mistake one for the other.

[Gary B.]

3916141: weak-kneed & $50 more expensive; bummer *NM*

[Joe L.]

Re: 3916141: weak-kneed & $50 more expensive; bumm

Gary-----

Yes, but it has a configuration very similar to many fan clutces of the period and pretty much exactly correct for those 68-70 applications which originally used the 3916141. So, for those that subscribe to the theory that original configuration is all-important, the fact that this clutch is still available is virtually a "drem-come-true". As far as FUNCTIONALITY goes, though, the 3916141 is not as up to the task as some of the 71+ clutches and, particularly, the ones previously described.

There were, however, some of the 71+ fan clutches that, while being reconfigured for the 71+ hub/fan configuration, were pretty much performance equals of the 3916141. It's just that in the 71+ period, there were a few clutches that offered much better cooling performance than ANY pre-71 clutch. So, while the 3916141 had 71+ performance "counterparts", the 343721 and successors had NO 55-70 performance "counterparts".

That's just how it goes "moving west".

[Tom M.]

Re: Best Replacement Fan clutch for a '74 BB w/air

Joe, Thank you very much for all the info, from the sounds of it though, it looks like I am going to need a fan also, Iam going to actually retro fit the a fan and clutch to a '67. And just like your recomendation, theese are supposed to be the best out there from what I have got from other sources, it just makes sense around here when it only pushes 100 for a very short time to switch back and forth between this more efficent set-up and the original as needed.

Thanks Aagin,
Tom McCabe

[Joe L.]

Re: Best Replacement Fan clutch for a '74 BB w/air

Tom-----

If you're retrofitting it to a 67 big block, you'll need to change the fan. You'll also need to use the smaller (1-3/8" bolt circle) hub mounting pattern. And, you'll need to use a 5/8"-to-3/4" bushing that, hopefully, will come with the fan clutch. If not, you can get one at a good hardware store, although you may have to shorten it. DO NOT USE THIS FAN CLUTCH (with its 3/4" pilot hole) WITH YOUR ORIGINAL PULLIES AND WATERPUMP WITH 5/8" PILOT/PILOT HOLES WITHOUT USING A PRECISION BUSHING AS I DESCRIBED. To do so, is "courting disaster".

Also, as I mentioned previously, if the car is a 1967 small block, I don't recommend the described fan clutch with a stock waterpump. A conversion can be done, but it's a LOT more involved.

You can use fan GM #342715. This lists for about 100 bucks but it will work well and even have a similar appearance to the original fan (although this has 7 blades).

[Tom M.]

Re: Best Replacement Fan clutch for a '74 BB w/air

Joe,

Thanks again, for all the info. This should make the conversion alot easier. Now as long as the local parts guy can find them, I will be in business.

Thanks Again,

Tom M