# fan blades for A/C '67 GTO



## TommyG67 (Dec 17, 2009)

Now that my big overheating problem seems to be solved, I can actually drive the car on a 100 deg day without boiling over, but I do gain 15 deg sitting at idle at a long stop light. I started looking at improving idle airflow through the radiator and I came across a “new” (to me) fan blade (for a clutch fan) and wondered if it would improve idle airflow.
What I came across looks quite different from the one that came on my ’67 GTO when I bought it (and is still on the car). This “new” fan blade is listed as being for a ’65-’67 GTO with A/C and mine is originally an A/C equipped car. 
The 18" dia. one I found has 7 blades and is listed for A/C cars - it has very sharply curved ends on the blades. I found it at https://www.opgi.com/gto/GBC0560/ 

The one on my car is 19"; has 7 blades and has a 2" pitch - the ends are not curved out like the one described for A/C cars. See attached pix (at least I hope they're attached....).

Do any of you have any knowledge of this kind of fan blade and how effective it is at moving air compared to the type I have? Anyone have one of these, by any chance?


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## pjw1967 (Mar 10, 2014)

I cannot speak to the fan you are looking at. I have a/c in my '67 and use the orig 7 blade fan. My car does have a Hayden heavy duty fan clutch. It also has this seal kit https://secure.amesperf.com/qilan/Detail_Web?part_num=P167&order_number_e=NDExNjQ2OQ==
&web_access=Y
I think Pontiac recognized the problem early on and came out with this kit. The fan can pull air from around the radiator as well as thru it. This kit helps increase the flow thru the radiator. The heavy duty Hayden clutch also helped my hot running issues.
Hayden - Fan Clutches and Fan Blades
Since you won't lose anything by installing the seal kit, I'd start there if you don't have it. A new fan clutch won't hurt either. Hopefully someone else has experience with the fan you are considering and will chime in.


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## TommyG67 (Dec 17, 2009)

Thanks for the reply, but a new H/D fan clutch and all sealed up around radiator & shroud was all part of getting it to the point where it is now. On the road - 75 mph on 100 deg day runs 195-205 (180 deg 'stat & A/C not on). Now on to the idle warm-up. One thing at a time, I guess.... will wait to get A/C working (need new compressor) until the idle temp is a bit cooler.


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## PontiacJim (Dec 29, 2012)

TommyG67 said:


> Thanks for the reply, but a new H/D fan clutch and all sealed up around radiator & shroud was all part of getting it to the point where it is now. On the road - 75 mph on 100 deg day runs 195-205 (180 deg 'stat & A/C not on). Now on to the idle warm-up. One thing at a time, I guess.... will wait to get A/C working (need new compressor) until the idle temp is a bit cooler.



Well, seems pretty good to me with those numbers. At 75 MPH, what kind of RPM's is the engine running. My Lemans with 3.23 gears & tall 29" tires would be near 3,000 RPM's at that speed- really a bit too much for these older engines to be running steady at 75MPH or above. They don't have all the aluminum like moder engines to help cast off heat. Your RPM's may be contributing to the heating. The cast iron engine holds heat and then when you slow down or come to stop & go/idle conditions, all the heat is going right into your cooling system.

Have the heads or block ever been milled? 

How close to the radiator is your fan? Also the fan, from what I have read, should be slightly out of the radiator shroud. If it is too deep, you could be whirling more air around than drawing it through the shroud opening as is supposed to be.

If you have an automatic, remember that your trans lines also go into the radiator which can add to everything. I always add a trans cooler to get the additional heat from the trans fluid out of the radiator. I also suggested this before, a product called "Wetter Water." 




I added the product to the 50/50 antifreeze mix (if you do your own mix, only use DISTLLED water, not tap water from your facet or garden hose- lot of minerals that will harm your cooling system over time). I have read that a 70/30, water to antifreeze will cool better, but will be problematic and prone to freezing in cold climates and you don't need a busted block.

With the 50/50 mix, 1 bottle of the product, and the fairly new 4-core (non-aluminum), the temperature when hot did drop about 10 degrees. A fluke? I don't know, but it did do something according to my temp gauge. 

Do a little research on the stuff or simply try it as it doesn't appear to harm anything. I will use it again when I get my project re-assembled and back on the road. :yesnod:


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## TommyG67 (Dec 17, 2009)

Thanks for your response, but my down-the-road overheating issue is gone now as a result of installing a Ron Davis Racing radiator (worth 30-40 degF !!!). 
You're right - 195-205 degF @ 75 mph on 100 deg days is not really a problem. Just to answer some of your questions, though..... RPM not an issue: a 200R4 tans, lockup converter, 3.55 gears and 245/60-15 tires net ~2400 rpm at 75 mph  The engine was all redone ~4500 miles ago and heads & block just "cleaned up", nothing radical. 
The fan blades are only out of the shroud by ~3/4" at the top and actually sit inside ~ 1.2" at the bottom - I have seen some '66-'67's like this and others not tipped so much - I have no ideal why. 

The question I posted was in regard to the fan blades listed by OPGI as being for A/C equipped cars. The very sharply curved tips made me wonder if they might clear more air out from the shroud - as you said, maybe the fan I have now is "...whirling more air around than drawing it through the shroud opening as is supposed to be." ? Since my car was originally an A/C equipped car, I'm thinking that this more "sculptured" blade shape might fix the problem you are referring to. I had hoped someone might have some experience with these.

Since open road temps are OK and prolonged idle is a manageable issue, I'm thinking maybe a bit more airflow at idle might do the trick. It appears that if I have enough airflow, the radiator will do the job.


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## PontiacJim (Dec 29, 2012)

OK, a little more research into your question/situation. A good search place to look is the Chevelle guys with their big blocks as many run them. If they can get their big bore engines to cool, then you want to take note of their suggestions.

"* ENSURE DUST SHIELDS ON UPPER A ARMS ARE PRESENT AND IN GOOD COND ,THAT AIDS PROPER UNDER HOOD AIRFLOW AT CRUISE SPEED TO HELP EXHAUST/PUSH OUT HOT AIR FROM UNDERHOOD."


"It is not ALL ABOUT the DIA. of the fan or Number of blades. But it IS ALL ABOUT The " PITCH of the blades ". The pitch decides on the amount of Cubic feet of air per. min. through your heat exchanger. A #3947 772 fan blade has a number, WHY? It was designed to work in concert with other G.M. items to keep a 450 H.P 454 LS-6 Cool. When all else fails, Use the stock and very cheep Chevrolet items that have a proven track record for over FORTY years.
Example: My 70-SS 468 Sta. Wgn. with A/C will NOT get to 200 degrees on my Mech. gauge with the A/C running or sitting in traffic.
My cooling system= 100% vintage 1970, Down to the 811TX water pump. I have no intention of re-inventing the wheel.
Go back and rethink your issue. Cooling is about details--Timing-Carb settings--ALL the under hood items that your car came with."

"I finally located a 7-blade 19 inch fan off a 72 chevelle that was a factory ac car. It made a noticable difference in how much better it cools when at a stop. It has the curved blades just like the 772 my buddy has on his big block, vs the flat 6 blade I was using. I would also like to note that my gauge was off 5 to ten degrees and running cooler than it showed. Anyhow it now reads around 200 to 205 when testing it at a dead stop for over 15 minutes with the ac running. So with the gage being a little off I would say I'm doing 180 when cruising and 195 after stop n go driving.
My setup is now a 3 row aluminum radiator, 71 shroud, 19 inch curved blade fan, hayden 2747 clutch, stock hd water pump, and Autozone #15356 160 degree stat with one relief hole drilled."

" * Where & how did you verify your gauge temperature was off 5-10 deg? (Did you maybe use a hand help Digital Thermal temp gun on stat housing or intake?)
Also, What temps did it used to run with the prior 6 blade non stock type fan you were running at cruise & at idle in traffic vs with the gm clutch fan you just installed with HD hayden fan clutch keeping temp in perspective when it comes to the difference you said your temp gauge has?
I get the feeling you may be comparing intake/stat housing temps to in head temps where there is often a 10-20 deg temp difference between those areas for obvious reasons.
If your motors temp sender is in the head, higher in head temp readings are likely as compared to intake/stat housing temp readings."

"I just ordered a 19" Ford big block clutch fan. It has the curved tips just like the 772 fan but is larger and should fill my 71/72 fan shroud much better. Also changing the HD clutch to a severe duty. Not sure I will do a direct A to B comparison between the two fans, depends how bored I get. I got antsy reading your post about the 19" fans, so I got one from a guy locally. Looks just like the 772, only bigger. Just got home, excited to put it on, and guess what, too big for my little shroud. Back to the drawing board. Need the 17 1/2 or 18". Point of story, make sure you guys have room for a 19"."

"My car had a shroud that only covered 2/3rds or so of my stock re-cored HD radiator, and a 17" flex fan. I found an early 70's Impala at the local junkyard that had the HD cooling system, so it had a 19" 7 blade clutch fan.I ordered the correct shroud, that covered the whole radiator core. Keep in mind the motor will rock when you rev it. Make sure the 19 inch fan will clear. It may clear at idle but may hit under acceleration. In a nutshell, if everything was "right", the 19" fan will clear easily. Mine has about 3/4"-1" clearance between fan blades and shroud, and fan blades are easily halfway into the shroud, which should be perfect." 


"INSTALL A HI FLOW #15356 STAT FROM AUTOZONE,ITS A TOUGH STAINLESS STEEL UNIT. DRILL AN AIR BYPASS HOLE IN IT.
I TESTED 160/180/192 DEG STAT IN STD AND HI FLOW DESIGN. AUTOZONES HI FLOW VERSION WITH STD DESIGN OPENING MECHANISM IS MUCH LESS PRONE TO MALFUNCTION THEN THE HI FLOW HI PERF STATS ON MARKET TODAY.
THE #15356 /160 AUTOZONE STAT DID THE BEST OF ALL THE STATS I TESTED IN STABILIZING MOST SETUPS ENGINE TEMP (SBC OR BBC IN DIFF PERF LVLS) AT APPROX 180 +- FEW DEG AT CRUISE DEG IN 90 DEG OUTSIDE TEMP,IN TRAFFIC 185-188 DEG ON AVG OFTEN NOT HITTING 190 TAKING IN HEAD TEMPS. STAT/INTAKE TEMP ON HOT SUMMER DAY WITH BE APPROX 10-15 DEG LESS.
WHY THE ISSUE WITH HI PERF HI FLOW STATS(MILODON/MRGASKET/ETC),WELL MY TAKE ON IT IS THE STD HI FLOW/HI PERF STATS HAVE A MULTIPLE PIECE MECHANISM THAT'S A MORE COMPLICATED DESIGN WHICH CAN BE AN ISSUE WITH POOR MFG NOT GETTING TOLERANCES RIGHT. KEEP IN MIND SOME OF THOSE STATS ARE NOW MFG OUTSIDE USA WHICH ARE THE ONES I PERSONALLY FOUND TO HAVE QUALITY ISSUES .
THE ISSUES WERE THEY WOULDN'T ALWAYS CONSISTANTLY/RELIABLY OPEN FULLY AND INCREASED ENGINE TEMP, IT WASN'T ENOUGH TO OVER HEAT MOTOR,BUT WAS ON EDGE AT TIMES.
IT WAS ENOUGH TO CAUSE ENGINE TO RUN HOTTER THEN IT SHOULD (10-12 DEG ON AVG)WHICH WAS A SNEAKY ISSUE TO TRACK DOWN AT THE TIME AS I HAD SEVERAL BRAND NEW STATS OF THE SAME DESIGN FROM DIFF MFG'S (LIKELY 1 MFG SUPPLIED MULT COMPANIES THAT PUT THEIR BRAND NAME ON THE STATS ). THEY WERE NOT ALWAYS OPENING FULLY WHICH DROVE UP ENGINE TEMPS AT TIMES, BUT WHEN I TESTED THEM IN POT OF BOILING WATER THEY OPENED OK AT THAT TIME.
I WAS LUCKY THAT THE SAME STAT I TESTED & REINSTALLED IN MY CAR LATER SHOWED LITTLE COOLANT FLOW IN RAD WHEN ID REV THE MOTOR AND LITTLE TO NO FLW AT IDLE AFTER IT HAD JUST OPENED. WHEN I TESTED IT IN BOILING WATER WHICH IS WHEN THINGS GOT BETTER FAST - SO THEY ONLY FULLY OPENED AT HIGH BOILING TEMPS WHICH IS NOT WHAT YOU WANT, YOU WANT THEM FULLY OPENED AT THEIR RATED OPENING TEMPS.
THAT'S WHEN I FOUND & TESTED THE STAINLESS STEEL HI FLOW FLOW AUTOZONE 15356/160 STAT THAT'S BEEN A GREAT PERFORMER FOR ME AND MANY GUY."


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## chief65 (Jun 6, 2011)

*Still need to drill hole*

Great thread and thanks for all the info PontiacJim. I have one question. I went out to AutoZone and bought one of the Thermostats you recommend. ( Actually when I got home I realized I got the 180F and not the 160F so I will exchange tomorrow.) The thermo has a brass check valve in it. See where my pen is pointing in picture. With this valve do I still need to drill a hole for air and if so is 1/8 inch dia good.
Thanks
Greg


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## PontiacJim (Dec 29, 2012)

chief65 said:


> Great thread and thanks for all the info PontiacJim. I have one question. I went out to AutoZone and bought one of the Thermostats you recommend. ( Actually when I got home I realized I got the 180F and not the 160F so I will exchange tomorrow.) The thermo has a brass check valve in it. See where my pen is pointing in picture. With this valve do I still need to drill a hole for air and if so is 1/8 inch dia good.
> Thanks
> Greg


No, that looks like it serves the same purpose and may be why that thermostat was recommended. I usually drill a couple 1/8" holes in the typical/standard type thermostat - so you should be good.

We have another discussion on a similar overheating problem. Check to make sure that your engine is not running lean. A lean running engine will have temps rising. It was learned that the idle screws were set too lean and needed to be backed out. You may even want to try this yourself to "fatten up" the carb a little. Today's gas with ethanol will run a little leaner, and if you build up the engine with a hotter cam, additional fuel may be needed to ward of a lean air/fuel condition. :thumbsup:


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## chief65 (Jun 6, 2011)

*thanks again*

Thanks for the answer PontiacJim. I exchanged the 180F thermostat for a 160F thermostat today and picked up my new vacuum advance part number DV1810 I think it was as recommended on another thread. 


And beleive me...I know all about NOT forgetting to check for a lean idle. I know you have posted on the thread "Rebuilt 455 in 66 GTO overheating"... That is my son!!!!!

Now since this thread is about fans. Am I crazy or did declucthing fans used to be different. My fan of choice is a declutching fan and a 7 blade fan. But with todays fan clutches it is hard to tell if it is working or not. As I recall back in the early 70's when the motor got hot and the fan clutch came on you knew it!! I had a 1970 454 Vette. The grills in those cars were small and sitting in a long traffic jam the temp gauge would slowly go up. But then all of the sudden the fan kicked on, it sounded like a turbo prop, the engine RPM would drop 200 rpm and soon the temp would come down. If you had your arm hanging out the window you could feel the heat. Also on a hot day after stopping for gas the fan would be on when you left the gas station. It would usually turn off in 1/2 mile. Does anyone remember a clutch fan working like this?? Does the Haydon clutch do this??


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## Lemans guy (Oct 14, 2014)

I have a 66 lemans AC car, the 7 blade fan does not have curved tips but cools great. 67 GTO fan probably the same. The fan clutch is important as well. The one you want is the "thermostatically" controlled clutch, it has a little metal spring on the front, just like a choke spring. When it gets hot it activates the clutch and fan regardless of rpm. The rpm only fan activates at lower rpm. But some guys set a high idle rpm and that may effect clutch operation.

Mentioned this on the other thread as well, timing and fan operation both have an effect on idle cooling, of other things too as discussed by the gang.


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## chief65 (Jun 6, 2011)

*This is my fan of choice*

This is the fan I usually use and was the fan on the 66 GTO before the 455HO. Of course we now know overheating was not a fan or fan clutch problem.


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## Shooter (Nov 7, 2015)

Just saw this thread. O.K. the question of the century - does the fan on a Pontiac spin clockwise or counterclockwise? The fan clutches can be ordered either way. What about the fan itself, it there a clockwise and counter clockwise fan?


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## Shake-N-Bake (Jun 16, 2015)

Shooter said:


> Just saw this thread. O.K. the question of the century - does the fan on a Pontiac spin clockwise or counterclockwise? The fan clutches can be ordered either way. What about the fan itself, it there a clockwise and counter clockwise fan?


While looking at the front of the engine...the fan turns clockwise.

Sent from my XT1585 using Tapatalk


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## Shooter (Nov 7, 2015)

Thank you!


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