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cooling system

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by muscle, Apr 26, 2005.

  1. muscle

    muscle 1/2 ton status

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    Hey guys I have a 400 sm block engine I rebuilt recently and I was wondering what to do about the radiator. I use the truck as a hunting rig and I creep alot. This engine has heated up before while creeping although when driving at normal speeds it does great. I used a 4-core radiator, direct fan w/o clutch. I know that 400's are notorious for heating up.

    That setup was on my 1977 blazer and I am currently placing the same motor, freshened up into a "new rig" I am building up as the latest hunting rig. It is a 1984 Jimmy. The problem I have is the jimmy had a 305 with a 2-core radiator, and the 4-core, out of the '77 will not work with the newer front clip bracketry. (upper mounts and shroud not compatible)

    So I have a 4 core with shroud and brackets out of a '77 and a 2-core with its brackets out of an '84. Should i just look around the junk yard for a set of brackets and shroud for the 4-core if they made such a thing, or do you guys think the 2-core will suffice?

    If needed i can provide some pics as well

    Any other suggestions on keeping my baby cool i would appreciate too :D
     
  2. cwn anwyn

    cwn anwyn 1/2 ton status Premium Member

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    Might try replacing the fan with this . I havent put it on my 84 yet, but thats the way Im going.:grin:
     
  3. muscle

    muscle 1/2 ton status

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    the winstar thing looks like its ok but not for me. it looks kinda boggled together the way its held together with cabinet straps and stuff. :hack:

    plus haveing a ford part on my chevy may jinx it, lol. not ruling out an elect fan set up made for older chevys tho.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    The upper radiator brackets and shroud should be pretty easy to find. I'd use those.

    You are in AZ, do you have to worry about freezing at all? If not, stop using antifreeze if you do, and look at the products that work to inhibit corrosion and use those instead.

    Nothing wrong with a "direct fan" (is that the stock clutchless one, or a "flex fan"?) for creeping, but pointless for freeway travel. If it were me I'd go with a heavy duty fan clutch and make sure you get a 7 blade stock fan.

    A better water pump won't hurt, since you already have heat issues. I know some of the aftermarket pumps are made to move more water at lower engine speeds, so if you can find one reasonably priced, that would be worthwhile too.

    Really depends how hot it got, 220* or so isn't outrageous for a small block, and with 400's running hot anyway, I wouldn't sweat it too much. I also wouldn't try running a 2 core in it unless you just want to play around and test it. 2 core that came with my parts cooled my 350 fine, but replaced it with a 3 core when I rebuilt the motor.
     
  5. muscle

    muscle 1/2 ton status

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    I live in az but AZ isnt all desert. Im at 6500' elevation in Eastern AZ and yes it gets very cold here in the winter. lows average 15 to 20 and many below zero occasions.

    It is a flex fan and you recommend upgrading it to a 7 blade? I thought clutch fans would actually spin the fan slower at idle or creeping speeds.

    The engine got as high as 225. She wants to crank harder when she gets that hot if i shut it off for a sec.

    I should go look for that year in say a 3/4 ton pickup at the junk yard to scavenge its shroud and brackets if it had a 4-core set up?

    thanks so far for the replies.
     
  6. TorkDSR

    TorkDSR 1/2 ton status

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    is 225 really that hot....?
     
  7. mouse

    mouse 1/2 ton status

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    I would definitely go with a four core rad with a 400. I'm not a supporter for electric fans, a good, heavy duty clutch fan has always worked better for me.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    0* rating with antifreeze is something like 40% antifreeze, run the lowest mix necessary. I was running about 35% this year and was into the teens multiple nights with no problems.

    Clutch fans lock up when the engine temps dictate, so difference in effectiveness at that point vs. flex fan is 0. When the engine is cooled adequately (like cruising) it stays unlocked which "frees up" some power and makes the radiator flow through cooling more efficient at speed.

    Even GM knew about the hot start issues, some vehicles (80's monte carlo's for instance) had some sort of "fix" (TSB?) that installed a fan to cool the carb when the engine was shut down. :)
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    GM decided 240* was the point when the later 350's needed additional cooling (secondary fan comes on at that temp) so I don't think 225* is too hot, but if you are having hot start problems, it might be something to consider.

    Then again, a phenolic spacer or something *might* help, if it's not underhood temps themselves that cause the problem, as opposed to manifold temp.
     
  10. muscle

    muscle 1/2 ton status

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    Hmmm well you learn something everyday. I did not know that clutch fans locked up at a certain temp. I just tought they were for ease on the water pump and added hp. Ill definately add a good clutch and fan whe she gets stabbed into the jimmy.

    The hot start may also be a hot starter. I plan to sheild it a bit from the header.
     

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