# 66 gto clutch fan



## tonyli (Aug 14, 2013)

I have 66 GTO 389 factory A/C car. I bought the car with an aftermarket fan blade. I just wanted to know the OEM number and or some specifications about the fan. Can I use a non factory air fan are lengths and pitch of blade different? are stock versions better than the after market.Thanks


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## pjw1967 (Mar 10, 2014)

I mucked around with different flex blades and clutches after my wife drove over the fan from my '67 with a/c/. I found a replacement 7 blade at a swap meet. I got a heavy duty Hayden fan clutch. 1966 GTO 7 Blade Fan | eBay
This one says it is 18.5 in dia. I am pretty sure my '67 is 19.5 in dia. The Ames catalogue says to use a certain shroud for a fan of 19.5.
Most of the replacements I have seen are 6 blade flex and 17 in dia. For max pulling you want a properly spaced shroud with the correct dia fan. Hopefully someone will weigh in with some specifics on the dia.


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## 67Twistytee (Feb 24, 2014)

For 66-67 a/c cars, a black plastic shroud #978375 was used with the 19 inch fan. The shroud has an inside diameter of 21.5 inches and the seven blade clutch fan is 19.5 inches with a 2.25" pitch (#9784546). There was also another type of shroud used and 18" fan for the trailer package but it's not common and wasn't used with factory a/c. 

IMHO - the 19.5" stock fan with the Hayden clutch mentioned by pjw1967 is a tough combo to beat if the rest of your cooling system is in order and your timing is set right. You can also step up to the Hayden severe duty clutch (#2797) but I don't think it's necessary if the balance of your system is working as designed. 

If trying to get the correct fan spacing with the shroud, I recommend weather striping the shroud perimeter rather than using a spacer on the fan. The extra length and weight of the clutch fan will shorten the life of the bearings in your water pump. Strive for 2/3 in 1/3 out on the fan.


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## pjw1967 (Mar 10, 2014)

Twisty, thanks for mentioning timing. It took me a long time to tumble to that. Main symptom that I experienced was the faster I went, the hotter the engine became. Once that was fixed (9 deg BTC), richening the mixture a tad helped a little too.


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## geeteeohguy (Feb 2, 2008)

I second what Twisty said. You want a factory 7 blade 19.5" fan with a Hayden clutch, and you want to run a shroud. You want the fan blades half in, and half out of the shroud when installed. The stock non-ac fan for these cars was an 18" clutch type with curved tips. Side by side with a 19.5" fan, the 18" looks absolutely tiny. These fans show up on ebay.....I picked one up for $25 about 4 years ago.


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## tonyli (Aug 14, 2013)

Thank you guys for your help. I have a 6 blade 18" aluminum fan. The car has a full metal shroud with a 21 to 21 1/2" inside diameter. It runs a little warm when sitting in traffic on a hot day about 200 to 205. But i just wanted to get it back to OEM. it did have a trailer hook up at one time but i think that was put after the dealer. it is not an option on my car in the PHS. The 19.5 fan does not have the curved blades?


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## 67Twistytee (Feb 24, 2014)

Stock ac fan has curved blades shaped like shovel buckets. See attached pic I borrowed from eBay. Honestly, 200 - 205 in traffic on a hot day is nothing to worry about. These cars don't get in to the red zone until 230-235. The correct fan and shroud may help (and would also get you back to OEM), but those are reasonable temps when the car is not moving in traffic and less air moves through the radiator. If you go with a stock 19.5" fan, I recommend getting a repro plastic shroud for ac cars. They're expensive ($100+) for molded plastic, but it will ensure you have adequate clearance around the fan. If your metal shroud is less than 21.5", you don't want to risk metal on metal contact. 

There's plenty of threads on here regarding proper cooling so I won't repeat them all here. Per the other comments, exhaust temps from improper timing play the most important part of keeping your engine cool. If you're running anything near original compression on today's gas, it's hard to stay cool and not get into spark knock. Most of these cars like 12-14 degrees initial timing which often requires lowering compression. Running them with retarded timing really kicks up the heat.


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