1966 350hp with AC fan - 5 or 7 blade?

[Patrick H.]

Hello All,

Could anyone verify for me the type of fan blade that belongs on our 66 350hp with AC car?

The Judging Guide specifies a 7 blade fan. Fine, but the repops are not correct and originals don't seem to be growing on trees. Then, if you read Noland's book he references two five blade fans for the 1966 C60 option, one the base and one the "optional" 5 blade. Of course, 5 blade fans of at least one of the two varieties are much easier to obtain.

Is the JG incorrect on the 7 blades? Is Noland incorrect on the 5 blades? Unfortunately our car came with no fan whatsoever, so it can't help me decide.

Thanks,

Patrick

[Michael H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Patrick,

This whole A/C fan issue for 63-67 is quite confusing but here's some info on it. The 66 AIM lists two different part numbers. One is shown as "optional". The first is 3789562 and the second "optional" number is 3863137. There's no mention of blade count for either but I know the 3789562 is an 18" 5 blade.

Here's what the May 1966 printing of the parts book shows.

63-64 Corvette W/AC (1st design)
66 Corvette W/AC (2nd design).. 18" dia 5 blades...3789562

64-66 Corvette W/AC (1st design).. 18" dia 7 blades...3853943

So... if you have an early 66, it looks like your car probably would have had the 7 blade 3853943 but if you have a late car, it would have had the 5 blade 3789562. I don't know what would be considered early/late as far as time build but at least you now have some info to work with. If necessary, I can try to scan the page from the 66 parts book for you.

The 7 blade looks like it was Corvette only and would be difficult to find but the 5 blade "562" was used on many pass cars with AC so it should be a lot easier. Hope this helps....

Hanson

[Jack H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

When the AIM book calls out P/N the one or more [OPT] numbers below it, that's telling you Chevy had two suppliers for the same part that they elected to track separately instead of treating as identical and warehousing in a common inventory bin, mixed, together. You'll find this same designation treatment on the fan clutch for MY cars where Eaton and Schwitzer (coil and bar) were issued separate PN's but assy folks could mix & match as well as on turn signal flashers (typically Signal Stat and Tung-Sol)....

It doesn't mean the 'optional' fan was for a car configured with orderable options. To find out if a given option impacted the fan used on the engine, you turn to that specific option section in the AIM (like C60 for air conditioning) and see if a different PN is called out to replace what was used on the base car. This call-out can either be in the assy pictorial pages associated with the option or in the option's 'boiler plate' with a reference along the lines "installs the same as production" when there was no need to have drafsmen create a specific pictorial.

Beyond that, what's the specific difference between this GM PN and that one, you need access to the drawing system to pull the individual drawings and take a look-see. Typically, when one 5-bladed fan was used for the base car and another was called out for C60, the difference was in the length/width of the blades on the spider and/or their 'attack angle' to deliver different air flow rates....

[Michael H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Jack,

You are exactly right. When I listed the "option" fan, I wasn't refering to the C60 option. I only used the word "option" because it was in the original print and on the AIM page. I probably shouldn't have mentioned the word "option" because it would have been, and was, confusing.

The info and part numbers that I provided are from the C60 parts lists and not the base engine parts list. You are correct, the base engine fan is a totally different number, a 3770529.

[Patrick H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Mike,

Our car is about 20800, built April 26th, so that would tend towards late.

That would mean a 5 blade fan would be acceptable. Now if I could only convince the judges.....

Patrick

[Michael H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Pat,

I agree. If the parts book showed the changed by the May printing, I would think the actual part was changed in production prior to that time, possibly as early as a few months before your car was built. If you would like, I can either scan and post that page of the parts book or send it directly to you. I would think if the judges were presented with a copy, they would have to give you the benefit on this one??

As jack Humphrey pointed out tho, this 5 blade A/C fan should not be confused with the standard 3770529 non A/C 5 blade. They may look similar but their not the same.

[Wayne W.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Just from observation and with no other documentation , the usage of the 7 blade fans was on cars with automatics and or very high speed rear gears like 3:08.

[Michael H.]

Re: 1966 350hp with AC fan - 5 or 7 blade?

Wayne,

Some of the paperwork I'm digging through now is indicating that the 7 blade was removed earlier in 66 production than I originally thought and was replaced with the 5 blade. The 7 blade seems to have been removed entirely and even the assembly manual makes no mention of it's part number. The 3789562 part number in the AIM is definitely a 5 blade. I now have a scan of the May 1966 parts book that clearly shows the early 7 blade and the 5 blade that replaced it. I'm convinced the 7 blade 3853934 made it's appearance in early 64, was used all through 65 and was replaced with the original 63-early 64 3789562 5 blade.

[Michael H.]

Re: May 66 Parts Book *NM*

[Patrick H.]

Thanks!

Thanks Mike and Jack for the information!

Now to find the correct 5 blade fan....

Patrick

[Peter L.]

Re: Thanks!

Patrick, et. al. - Please check out the most recent version of the 1966 Corvtette TIM&JG. You should find the information you need. The Section has been revised and updated based on considerable research on "original" C60 sb '66s, along with the AIM, and Parts Books. There have been two fan blade assemblies identified. Both have 5 blades and are 18" dia. Hope this helps and if you wasnt more info give me a shout. Pete

[Peter L.]

Re: 1966 Corvette TIM&JG

Patrick - The most recent 1966 TIM&JG is Spring 2004 - Fourth Edition. Check out Chassis Section 5 ENGINE COOLING SYSTEM, p. 102. NOTE: It does indicate that "There are undocumented cases of 7 blade fans used in air-conditioned cars." So if you have the documentation, a 7 blade assembly it could pass muster; but otherwise an 18" dia, 5 blade fan assembly; either P/N 3789562 or 3863137 would be what I'd look for. Pete

[Patrick H.]

Re: 1966 Corvette TIM&JG

Thanks Pete.

I did wonder if this was in the brand-new edition, but I of course purchased the 3rd Edition just this past winter. Too bad you can't get a "trade-in value" for TIM&JG's.

Then again, maybe I can sell if for $50 on eBay.

Patrick

[Michael H.]

Re: Thanks!

Well Patrick, looks like we learned this one the hard way and everyone else already knew the answer. Oh well, now we'll always remember which fan is correct.