Radiator Fan

[enaberif]

Trying to figure out if this fan would work on my truck? 74 chev with a sbc 350.

[fxrsrider]

maybe it's the angle of the photo...but it looks like that fan is either missing a blade or has been the victim of an impact of some sort.

remove the fan clutch and we can tell you if the bolt pattern is correct.

Long or short water pump?

[LTZ C20]

Some fan have the blades spaced oddly to make it quieter. If they were all equal, it would sound like an airplane.

[HAULIN IT]

This post just made me chuckle...made me think of something I made jokes about quite often years ago, back when just about every car you worked on had a mechanical fan. I'm convinced (not really, just part of the rant) that a young guy started in 1950 with GM in the "Cooling Division" & after a few days on the job...looking at this basic cross 4 blade fan he thought: "How am I ever going to make it to retirement here?" To keep his job, he set out to make "new" fans...curved blades, folded blades. Later 3 blades (in the early Astro vans) MANY 5 & 6 blades, even some of those big Buicks & Caddy's in the '70's had 7 & maybe even 8! more curved blades, big spaces, no spaces (7 blades!) 14", 14 1/2" 16" 18"...this clutch, that clutch & so on.
 He retired around 1990 & they said: "Now what are we going to do? Fred the fan man is Gone! Some electrical wiz kid stood up & said: I'll take that department over" ...the rest is history!

 Seriously, I'd love to spend a bunch of time with a pile of fans on a dyno & air flow readings (which is what GM did) to see what amount of difference some of them made...I bet MANY of them  are so close it really wasn't worth the bother, however they needed .2 MPG or something to get where they needed to be. Lorne

[fxrsrider]

This post just made me chuckle...made me think of something I made jokes about quite often years ago, back when just about every car you worked on had a mechanical fan. I'm convinced (not really, just part of the rant) that a young guy started in 1950 with GM in the "Cooling Division" & after a few days on the job...looking at this basic cross 4 blade fan he thought: "How am I ever going to make it to retirement here?" To keep his job, he set out to make "new" fans...curved blades, folded blades. Later 3 blades (in the early Astro vans) MANY 5 & 6 blades, even some of those big Buicks & Caddy's in the '70's had 7 & maybe even 8! more curved blades, big spaces, no spaces (7 blades!) 14", 14 1/2" 16" 18"...this clutch, that clutch & so on.
 He retired around 1990 & they said: "Now what are we going to do? Fred the fan man is Gone! Some electrical wiz kid stood up & said: I'll take that department over" ...the rest is history!

 Seriously, I'd love to spend a bunch of time with a pile of fans on a dyno & air flow readings (which is what GM did) to see what amount of difference some of them made...I bet MANY of them  are so close it really wasn't worth the bother, however they needed .2 MPG or something to get where they needed to be. Lorne

  Laughing my rear end off.....so true!

LTZ C20
Thank you for the insight....I had no idea.  Come to think of it, mine does sound like an airplane.....but the stroked block, my particular cam, headers, and exhaust are so loud no one would readily notice 

[LTZ C20]

Your welcome, if I remember correctly, my original fan had 6 or 7 blades, and they were spaced so that the space between blade 1 & 2 was 1 inch, 2 & 3 was 1 1/2, 3 & 4 was 2 inch, etc etc. Not exact measurements but at the end, the space between blades 6 or 7 & 1 was the biggest.

[BBM3]

That looks exactly like the fan on my '75 350 K10 (minus the crusty stuff).

Off Topic:

Times were good for Harold the high beam switch guy too.
Harold was responsible for the same floor mounted high beam switch for decades making only minor changes during his long and illustrious career.
Then came Steve the steering column guy who one day proclaimed “I can move Harold's high beam switch from the grungy floor to my new super awesome turn signal stalk”.
Sadly, Harold retired a broken man however Steve continues to pack more stuff into his turn signal stalk than Harold could have ever imagined. Just ask Wilbur the wiper switch guy, Christopher the cruise control guy, and Horatio the headlamp switch guy.

[LTZ C20]

That looks exactly like the fan on my '75 350 K10 (minus the crusty stuff).

Off Topic:

Times were good for Harold the high beam switch guy too.
Harold was responsible for the same floor mounted high beam switch for decades making only minor changes during his long and illustrious career.
Then came Steve the steering column guy who one day proclaimed “I can move Harold's high beam switch from the grungy floor to my new super awesome turn signal stalk”.
Sadly, Harold retired a broken man however Steve continues to pack more stuff into his turn signal stalk than Harold could have ever imagined. Just ask Wilbur the wiper switch guy, Christopher the cruise control guy, and Horatio the headlamp switch guy.

LMBO!!! You did forget tho, at first they did not have alot of faith in Steve because the steering column switches kept breaking at the base when they were the fully plastic deaign. Also, Wilbur got a big raise a couple years ago when he figured out the "rain sense" automatic wipers.

[HAULIN IT]

That looks exactly like the fan on my '75 350 K10 (minus the crusty stuff).

Off Topic:

Times were good for Harold the high beam switch guy too.
Harold was responsible for the same floor mounted high beam switch for decades making only minor changes during his long and illustrious career.
Then came Steve the steering column guy who one day proclaimed “I can move Harold's high beam switch from the grungy floor to my new super awesome turn signal stalk”.
Sadly, Harold retired a broken man however Steve continues to pack more stuff into his turn signal stalk than Harold could have ever imagined. Just ask Wilbur the wiper switch guy, Christopher the cruise control guy, and Horatio the headlamp switch guy.

I love it! Oh, the stuff we think of to make it through the day! Wouldn't you love to spend some time as a fly on the wall in some of these engineering rooms?  Thank You for the laugh...even got the new headlight switch guy's name "correct"! Lorne

[enaberif]

Well that is the thing. I don't know if the original fixed fan is what should be on the truck. And the fan I got is similar to the one I posted. I know the fan blades are opposite to one another and I had to take off the fixed fan because it was over cooling my truck. I've tried to find pics of trucks of the 73-80 era with clutch fans but they don't seem to exist and I can't find any around where I am.

Also I've learned that any truck that uses serpentine is reverse rotation and the same thing applies to the clutch.

Said fixed fan.

[fxrsrider]

Well that is the thing. I don't know if the original fixed fan is what should be on the truck. And the fan I got is similar to the one I posted. I know the fan blades are opposite to one another and I had to take off the fixed fan because it was over cooling my truck. I've tried to find pics of trucks of the 73-80 era with clutch fans but they don't seem to exist and I can't find any around where I am.

Also I've learned that any truck that uses serpentine is reverse rotation and the same thing applies to the clutch.

Said fixed fan.

Over cooling?  hardly seems possible.  What is the degree rating of your thermostat?

The direction of the blades indicates the direction of rotation.  A standard long water pump will rotate clockwise.  Your fan clutch needs to match the rotation of your fan (clockwise or counterclockwise).

It is not true that "any truck that uses serpentine is reverse rotation."  GM performance serpentines do use a reverse rotation water pump....and therefore requires a counterclockwise fan and fan clutch.  But there are many, many aftermarket serpentine systems.  Several companies make serpentine systems that utilize the standard long or short water pump and do not require a reverse in direction.

This whole fan situation is really the most untrivial part your drivetrain....albeit important.  The fan bolts up to your water pump pulley with four nuts or bolt.  Just put the fan on, start your truck, and determine which way the air is moving.....if the air is being pulled through the rad, then you're good.  If the air is being pushed through your rad, then you need a fan that runs in the other direction.  Don't worry about the fan clutch for now.....once you know the direction then you'll know if the clutch works for your application or not.

Note: you can't just take a fan and turn it over to make it work in the opposite direction.

[enaberif]

Yes over cooling. With that fixed fan on my truck I could not get the thermostat to open AT ALL. I had to pull the fan off to get it to tempreature high enough to open the thermostat. I am using a stock 195 and with the fixed fan the highest the thermostat would get is around 180. This was all verified with a infrared thermometer gun.

When I pulled off the fan everything worked as it should without a single hitch so that told me the fan is overcooling and not letting things get to where it needs be.

Regarding the fan yes I know that the fan needs to be specific but the fan pitch of the two fans I have is completely opposite. If I could see pictures of someones stock setup with a fan clutch it would be greatly appreciated because I'm spinning my gears right now.

You can even look at this fan http://www.summitracing.com/int/parts/hda-3618/overview/ from Summit Racing which says its a clockwise turning which would say that the fan with the clutch above is the correct one.

[Stewart G Griffin]

My 83's clutch mechanical fan has uneven spaced blades.  The 4.3's fan out of an 86 1/2 ton also had 3 blades.

[fxrsrider]

Yes over cooling. With that fixed fan on my truck I could not get the thermostat to open AT ALL. I had to pull the fan off to get it to tempreature high enough to open the thermostat. I am using a stock 195 and with the fixed fan the highest the thermostat would get is around 180. This was all verified with a infrared thermometer gun.

There's nothing wrong with your engine running at 180°F.  In fact, I strive for that as a running temp.  If the thermostat has no reason to open, then all the better.  If you are concerned about the water flow...in that you would like the coolant/water to be running through the whole system regularly, then put a 160° or 180° thermostat in.

I'm not running anything stock.  I have a higher displacement and a heavy handed street cam.  I run a mechanical fan on my long water pump with a new 4-core all aluminum Camper Special rad with a one piece shroud.  It all runs at about 183°F on average.  When sitting here in L.A. traffic on a 90+° day, I'll watch my digital temp gauge creep.....sometimes to 205°F.....that's when I start getting nervous.   As far as I'm concerned, the closer to 250°F, the worse.  IMHO, 180°-200° is an ideal operating temp range.  Overcooling?....no such thing.

[enaberif]

Well either way I need the thermo stat to open and I need to if the fixed fan about is correct of if the clutch fan is correct. Nobody seems to be giving me that answer.