BB Cooling Fan with A/C

[Gary J.]

In the fourth edition of the 1966 Judging manual there is a statement : "There are undocumented cases of 7 blades fans used in air-condition cars." This is under the Small Block title.

Under The Big Block title it list part # 3872792 for the fan.

Now the question - Were there any 7 blade fans used for a big block in '66 with A/C? If so what would be the part # of the fan?

Would the 7 blade fan help in cooling better in a big block with A/C than a 5 blade fan?

When did the 7 blade fan come about?

[Joe L.]

Re: BB Cooling Fan with A/C

In the fourth edition of the 1966 Judging manual there is a statement : "There are undocumented cases of 7 blades fans used in air-condition cars." This is under the Small Block title.

Under The Big Block title it list part # 3872792 for the fan.

Now the question - Were there any 7 blade fans used for a big block in '66 with A/C? If so what would be the part # of the fan?

Would the 7 blade fan help in cooling better in a big block with A/C than a 5 blade fan?

When did the 7 blade fan come about?

Gary-----


Were there any 7 blade fans used for 1966 L-36 with C-60? I don't know, for sure; I've not studied this issue. However, GM says that early 1966 Corvettes with C-60, regardless of engine, used fan GM #3853943. This was an 18", SEVEN blade fan. GM says that later 1966 Corvettes with C-60, regardless of engine, used fan GM #3789562 or 3863137. Both of these are 18", FIVE blade fans. The 3863137, if it was used, was a PRODUCTION-only piece, never available in SERVICE.

I doubt that the seven blade GM #3853943 would provide any significant cooling difference over the five blade GM #3789562 or the 3863137. I know that, intuitively, it seems that a seven blade fan should provide superior cooling than a five blade. However, there are a lot of other factors that enter into fan blade design which affect the amount of air it pulls. All things being equal, a seven blade will pull more air than a five blade. In this case, though, all things are NOT equal.

[Gary J.]

Re: BB Cooling Fan with A/C

Thanks Joe for the information. Now one more question.

In the 1966 Judging manual it list part # 3872792 as the fan blade assembly which is a five blade for a BB car. Is this fan used for a BB with AC also? This is the only part # it list for BB. Should the manual read for a BB non A/C the #3872792 is used and for a BB with A/C fan # 3789562 or 3863137 are used?

[Joe L.]

Re: BB Cooling Fan with A/C

Thanks Joe for the information. Now one more question.

In the 1966 Judging manual it list part # 3872792 as the fan blade assembly which is a five blade for a BB car. Is this fan used for a BB with AC also? This is the only part # it list for BB. Should the manual read for a BB non A/C the #3872792 is used and for a BB with A/C fan # 3789562 or 3863137 are used?

Gary-----


I'm not sure on this one since I have no even remotely recent experience. However, I can tell you that GM says that fan GM #3872792 was used only for 1965 L-78. They say that fan GM #3888366 was used for 1966 with L-36 or L-72. The 3888366 looks to me like a part number that would have been available for the 1966 model year, although it might not have been available at the very outset. The GM #3872792 and 3888366 are very similar. In fact, I don't even know what the functional difference is between the two.

I also THINK it's very possible that the 3888366 was used for some, most, or all 1966 L-36 with C-60 rather than the 3789562 or the 3863137.

[Gary J.]

Re: BB Cooling Fan with A/C

Thanks Joe, maybe some other will chime in as to what part number fan are on there BB cars with A/C.

[Peter L.]

Re: BB Cooling Fan with A/C

Gary - The NCRS 1966 Corvette "judging manual" is in the process of being reviewed and updated. As Joe mentioned, the #3872792 fan blade assembly was used only on the 1965 396s. During the review, the fact that the 65 396 fan blade assembly was listed for the 1966 BB fan blade assembly was noted and this should be updated to the #3888366 fan blade assembly that was used on all (both 1966 standard, non-A/C and those w/ C60) BB Corvettes. The #3888366 fan blade assembly is 17-1/2" dia, has 5-blades, and has 66 stamped on the front of the center support or "spider."

With regards to a 7 blade fan blade assembly being used in PRODUCTION on 1966 BB Corvettes, so far documented evidence has not been presented.

As far as 1966 sb Corvettes w/ C60, a very early build (Sept 1965 build, if I recall correctly) sb (Base Motor) w/ C60 was presented for Bow Tie at the 2008 NCRS National Convention. This car had a number of 1965 Corvette PRODUCTION C60 components including the 7 blade fan blade assembly. I was not involved in the Bow Tie judging. This is the first 1966 C60 Corvette that I have seen to support the statement of the 7 blade fans being used on 1966 C60 Corvettes but as far as I could see and tell the A/C components checked out.

Pete