One topic I have covered here before is how absolutely pathetic the design of the stock stamped steel fan is. What I have discovered about the stock fan is that it forces most of the air it moves outward, like a centrifugal blower, as opposed to actually pushing the air back toward the engine. The clumsy paddle-blades are raked back from the direction of rotation for some odd reason, which seems to contribute to this problem.
Result? On hot summer days, with the AC on, high-side pressures of the AC system climb to ridiculous levels (300+psi), and engine temps creep up as well. This eventually takes its toll on the R4 compressor, causing seepage out of the front seals. Replacing my fan clutch with a new GM clutch, and even a severe duty clutch made no difference.
So why am I discussing doing anything with a mechanical fan arrangement, rather than just going with an electric fan system? Well, I and GM both agree that for hauling heavy loads, a mechanical fan can't be beat for cooling power. Also, I just had an itch to see if something could be done to improve cooling without tearing the whole thing out.
The solution can be found in the GM truck line, where both V* engine and cooling continued to evolve. Most 1997+ GM trucks came with a nice 11-blade composite cooling fan that is a good sight better than what the 91-93 cars came with. Although they use a spin-on fan clutch, the bolt pattern for the fans themselves stayed the same. This is because GM was slowly phasing out the old metal paddle-blades and going over to what you see below.
Comparison between the original fan (top), and the 97+ truck fan (bottom):
The difference in performance between the two is very noticable. The new fan clearly moves more air, and in the right direction. AC pressures do not skyrocket. Engine temp is solid as a rock.
Only 2 drawbacks:
1. This new fan is slightly larger in diameter. There is more than enough space for it in the fan shroud unless your engine is sagging due to bad motor mounts
. It's not rocket science to tell. If your fan looks disproportionately low to the edges of the shroud opening, you need to replace those mounts. Eventually, even your stock fan will begin hitting the lower shroud.
2. You can hear
the difference in air being moved. It's not ridiculously louder than the stock fan, but when that fan clutch is locked the tightest, you'll hear it roar. Just listen to any 97+ full size GM SUV and you'll hear it in action.
Other advantages compared to e-fans? I got this fan from the local upullit for $7. I didn't add any electrical load to the system. I didn't have to radically change anything. Whole thing was done in less than 10 minutes.
It goes without saying that you should make sure your fan clutch is in good working order as well, and replace if necessary.