Radiator Fan

[enaberif]

Yah I replaced the radiator, thermostat and new coolant. Working on the fan now and glad to have you here bd and glad to know I should have a clutch fan.

Now I just need to find one.

[blazer74]

My 74 k5 also the staggered fan with the fan clutch.
Not sure if it is 5 or 7 blades tho, I'm 700 miles from it right now.


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[enaberif]

My 74 k5 also the staggered fan with the fan clutch.
Not sure if it is 5 or 7 blades tho, I'm 700 miles from it right now.


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Can you get me a picture of yours so I can have something to reference? Would be greatly appreciated.

[blazer74]

I will but it will be Thursday before I get home. Also it is factory original.


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[blazer74]

Will do but will be Thursday befor I get home.


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[Stewart G Griffin]

i just want to interject that i had a 79 blazer with the 4 blade fixed (350) and automatic.

The 79 truck info packet (in the tech section) shows the 350, 305, 267, and 250 straight six as having the 4 blade fixed fan.

[Stewart G Griffin]

Alright, it appears that automagics and/or air conditioned equipped trucks got the clutch fan while "standard" trucks got the fixed blade.  (i'm looking at the 74 truck info packet)

Too sleepy right now, will continue tomorrow.

i'm not trying to confuse the issue and start an argument;  i'm trying to learn as well.

[blazer74]

My 74 k5 also has A/C with the clutch fan 350 eng 350 trans.


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[bd]

GM Parts Wiki: 1973-1978 CKP Light Trucks 
Navigate forward and backward by clicking the page icons at the upper right and left of the GM parts page.  Peruse to your hearts content. 

[fxrsrider]

to say you "cant" over cool an engine is kind of a misstatement.  keeping the engine temp too low and the fuel wont conver into heat like it normally would. heat is energy released during a combustion,  so the cooler the engine runs the more heat that gets removed via water and cooled down in the radiator now and that heat is replaced by more heat from the next combustion. so if you have to remove heat it will get replaced by more heat and youre equivalently waisting energy.if we're talking intake temp thats a little different cause the cooler the more dense meaning more fuel you can add. the reason we have to keep the temps down is cause of metal problems and the most efficient temps would surpass the failure temp of most metals

  Agreed.  Such is why we seek to warm up our engine's before we drive.  My statement was meant relatively....as in yes, if one were to, say, maintain their engine bay full with glacier ice for the sake of cooling, then it is arguable that they are overcooling their engine.  Yes, engine heat is important to operational efficiency and yes, engine heat is different from intake heat.  In this case, however, we're talking about a mechanical fan on an sbc 350, no?  How a mechanical fan can overcool that size motor is a mystery to me.  Maybe it's that I live in a warm climate....and so my reference point is different than someone in Alaska, for example.  Nevertheless if there's an OE or stock mechanical fan out there that "overcools".....then I want one.

That said, I'm w Griffin now....and am going to just sit back and watch (and hopefully learn) this thread.

[rich weyand]

My 1978 350, no A/C, fixed blade fan, would never reach operating temperature during half the year.  The bleed on the thermostat was enough to overcool the engine with cold ram air through the radiator and the fan always running.  I went to an electric fan that only turns when needed, now no problem maintaining operating temps regardless of outside temps.

[enaberif]

to say you "cant" over cool an engine is kind of a misstatement.  keeping the engine temp too low and the fuel wont conver into heat like it normally would. heat is energy released during a combustion,  so the cooler the engine runs the more heat that gets removed via water and cooled down in the radiator now and that heat is replaced by more heat from the next combustion. so if you have to remove heat it will get replaced by more heat and youre equivalently waisting energy.if we're talking intake temp thats a little different cause the cooler the more dense meaning more fuel you can add. the reason we have to keep the temps down is cause of metal problems and the most efficient temps would surpass the failure temp of most metals

  Agreed.  Such is why we seek to warm up our engine's before we drive.  My statement was meant relatively....as in yes, if one were to, say, maintain their engine bay full with glacier ice for the sake of cooling, then it is arguable that they are overcooling their engine.  Yes, engine heat is important to operational efficiency and yes, engine heat is different from intake heat.  In this case, however, we're talking about a mechanical fan on an sbc 350, no?  How a mechanical fan can overcool that size motor is a mystery to me.  Maybe it's that I live in a warm climate....and so my reference point is different than someone in Alaska, for example.  Nevertheless if there's an OE or stock mechanical fan out there that "overcools".....then I want one.

That said, I'm w Griffin now....and am going to just sit back and watch (and hopefully learn) this thread.

Perhaps the term "overcooling" is being taken out of context but what else would you call it when you can't get your thermostat to open properly and allow the engine to run at an optimal temperatue?

I live in a cooler region and when the fan was running all the time the radiator would only be at 41* F and never go any higher so the truck could never run efficiently.

With a new rad, thermostat and fresh coolant my truck is cooling to a point where it won't run efficiently and I need to fix that which is going to be done by removing the fixed fan for a clutch fan.

[Irish_Alley]

No I don't believe over cool is the wrong term. But it can be taken a couple different ways. But like said the main problem is the fixed fan instead of a clutch fan.

[BBM3]

I think your plan to add a fan clutch is sound.
My '75 350 K10 does not have A/C, does have a fan clutch, and engine temps run rock steady once warmed up.

Here is a quote from the GM 1973 CK service manual:

"Automatic fan clutches, Figure 6, are hydraulic devices used to vary the speed in relation to the engine temperature. Automatic fan clutches are used with many engines, especially those equipped with factory installed air conditioning units. Automatic fan clutches permit the use of a high delivery fan to insure adequate cooling at reduced engine speeds while eliminating overcooling, excessive noise, and power loss at high speeds."

[Stewart G Griffin]

What was the original question?