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Super cooling for the AZ summer

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MaxPF, Jun 5, 2006.

  1. MaxPF

    MaxPF 1/2 ton status

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    Having been less than thrilled with my Blazer's cooling (temps of 220-235 on the trail with the AC on) I have decided to make some modifications. The PO already put a big-ass Modine 4-core radiator in it, and I have very thoroughly flushed the system. Since the A/C performance drops and head pressure shoots way up at idle, I have been messing with airflow. One problem is that the wussy stock fan just doesn't move much air at low RPM's (tes, the clutch is fine). So, what's a boy to do? Go down to GM and get a fan off of a late Duramax application! It's a 21 inch 9 blade fan with some seriously big, high-pitch blades :bow:

    The first thing you will discover if you try this is that the center hole and the bolt pattern on the Dmax fan is much larger than the gas motor fans. After an hour's worth of work I had machined myself a nice adapter out of 6061. Works like a champ, and this sucker moves a LOT of air, lemme tell ya :saweet: Minor shroud trimmi9ng was necessary, of course. :D

    Here's the Dmax fan complete with clutch next to the lame stock 5-blader:

    fan-r.jpg
     
  2. Rhinopkc

    Rhinopkc 1/2 ton status

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    I need one of those!
     
  3. chevy_addict

    chevy_addict 1/2 ton status

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    Post up your temps after you try it out on the trail. That is a monster fan!

    Dave
     
  4. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Does that one work with serpentine , or v-belts ? I am having a brain fart right now , and seem to think the waterpumps on newer stuff is reverse rotation :thinking:
     
  5. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    It appears to have the blades pitched the same direction.
     
  6. 4xcrazy

    4xcrazy 3/4 ton status

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    sure your clutch might be working, but is it a sever duty type of clutch??

    I have had to put one of these on just about all my rides to keep the temps down to where i like them, they really do help, never really had any problems after i did just this change.
     
  7. MaxPF

    MaxPF 1/2 ton status

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    It's a reverse-rotation fan. My ride is a 91, so it has a serp setup on it.
     
  8. MaxPF

    MaxPF 1/2 ton status

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    Yup. In town, the temps stay around 210, although you can feel the A/C slowly get warmer when you are sitting at a light in gear (500 engine RPM). The clutch and old fan were locked up and pulling air, just not enough.

    A little BG though. When I got the truck, it had no shroud and a dinky electric fan in front of the radiator. The PO claimed it stayed cool in the summer. :surepal: So, I ripped off the electric fan, then I went down to my friendly Chevy store and bought a new 2-piece shroud. With a little trimming I got it to fit the bigger radiator, but I noticed there was a lot of clearance between the stock fan and the shroud, and the fan sat completely inside the shroud, rather than half in, half out like they are supposed to be. Since axial fans spill a lot of air radially (i.e. off the ends of the blades), the fan was simply recirculating a lot of air inside the shroud rather than moving it out.

    So, I got the Dmax fan. It fits the shroud (after trimming :D) much better, having about 1/2" of clearance on the drivers side and about 1 inch on the pass. side (which is the side the engine torques towards, so it needs more clearance). Also, the blades are half in, half out like they should be. I'll get some pics of it in the truck and post em up later.
     
  9. MaxPF

    MaxPF 1/2 ton status

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    OK, so here's some more pics. The first two are of the fan installed with the shroud in place. The third is a pic that barely shows the aluminum adapter. The fan is attached to the adapter with four 3/8-16 button head allen bolts and metal lock nuts. The adapter is then bolted to the clutch with some longer-than-stock (due to the added thickness of the adapter) 10mm bolts and locktite. The whole thing fits like it was meant to be there :D. So far, cooling is great. Temps actually drop when I am stopped at a light, and A/C performance when idling in gear is much better as well. The only thing I noticed is that it takes the clutch an excessively long time to heat up and lock when starting cold. The engine will get to 225 before you hear the fan begin a gentle roar. Then, the temp plummets to 195 and stays there. Not bad, but I may go ahead and replace the clutch anyway, just to have all new stuff in there.

    P6050002-r.JPG

    P6050003-r.JPG

    P6050005-r.JPG
     
  10. mouse

    mouse 1/2 ton status

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    Impressive...looks like you could go into business marketing those!
     
  11. k5guyva

    k5guyva 1/2 ton status

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    Fan clutches tend to go bad after 3 years anyways. If you spray down your condenser with a mist from a garden hose, and the vent temps drop like a rock when your AC is on max, it's time for a new fan clutch.

    Your work does look nice. What you have is much better than what the PO left you with.
     
  12. K5er4Life

    K5er4Life 1/2 ton status

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    how much did the dmax fan cost you? That looks like a spectaular idea and would like something to cool my 454 down during those summer days out riding in the mohave desert.
     
  13. MaxPF

    MaxPF 1/2 ton status

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    The fan was $48 from my local friendly Chevy parts store :deal:.
     
  14. AZ79K5Project

    AZ79K5Project 1/2 ton status

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    Please forgive my ignorance...Machined an adapter out of 6061??? What type of adapter? 6061???

    Any vibration or balance problems at higher RPM's?

    I like the idea and I am going to copy it. That's once I understand what needs to be done.

    Nice work.
     
  15. 4xcrazy

    4xcrazy 3/4 ton status

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    your AC will always cool down much more when you do this, no matter how new/old the fan clutch is,,,you are cooling the condensor much better with water than air can do anyways. Not really a very good example, sorry:wink1:
     
  16. K5er4Life

    K5er4Life 1/2 ton status

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    6061 is the metal composition, it is aluminum. Its a custom adapter he machined, or had someone machine, so that way the clutch will bolt up the fan.

    Would you be interested in making another, I dont know what your times worth but I would be willing to pay more than your time and materials. If not I wonder how the clutch on the dmaxs look like, if I might be able to get the cluctch match up to water pump nose.
     
  17. MaxPF

    MaxPF 1/2 ton status

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    AZ79K5Project: Balance is fine. The adapter has a step which the big hole in the fan hub locates on, and the adapter irself locates onto the clutch just like the original fan. You cannot simply try to locate the fan off of the bolt holes, or you will almost certainly end up with an out-of-balance fan. The imbalance may not be noticeable, but it will eventually wipe out the bearings in either the clutch or the water pump.:doah:

    K5er4Life is correct, 6061 is a commonly used aluminum alloy, which I machined the adapter out of. I would machine another, but the machines I use are not mine. My buddy has a CNC machine shop, and I can use the manual machines (when they aren't being used for paying jobs, of course) for my own projects. If I were to make one for someone else, it would have to be at the shop's hourly rate (i.e. not cheap). If you have access to a lathe it is not difficult to make.

    The Dmax fan has a hub ID of 3.250", vs. 2.500" for the stock smallblock fan. The bolt circle is larger as well. The Dmax clutch is one of the spin-on types - the water pump snout is threaded and the clutch threads onto it, similar to the later Vortec gas motors. I know fan clutches are available in 6" and 7-1/4" versions, with smallblocks commonly using the 6" clutches. Perhaps the 7-1/4" clutches use the larger diameter fan bores, and one is available for a 5/8" pilot 4-bolt water pump (like ours). It is something worth exploring, since it would eliminate the need for the adapter. :thinking:
     
  18. k5guyva

    k5guyva 1/2 ton status

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    This is meant as a simple test for people with marginal fan clutches. Professional AC mechanics use it quite frequently. Sorry if you don't agree with it. However, it does work.
     
  19. 4xcrazy

    4xcrazy 3/4 ton status

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    so do they do the same thing to test if the electric fans are not pulling as much air as when they were new too?? on those vehicles equipped with them from the factory, and ONLY electric fans??

    hmmm.
     
  20. k5guyva

    k5guyva 1/2 ton status

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    Are you suggesting that electric fans don't fail?
     

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