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Too much heat

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mountainexplorer, Aug 24, 2002.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    I have a SB400 in an '85 Chevy that runs at 210 degrees most of the time, even cruising down the highway after dark with the heater on full.

    When I put the motor in, it had a new starter, which stopped working after 2 weeks. It would start fine when cold, but as soon as it got hot, it would draw too much power, and act like a dead/low battery.

    I replaced the starter, and last night, this second starter did the same thing. As I was working on it an hour after it was run last, the starter was still too hot to hold for long.

    The factory exhaust manifolds have a built on heat shield, but it still got hot enough down by the solenoid this time that one wire melted.

    I have a good 4-core radiator in the truck, but I believe the 400 to be .030 or .040 over. Anyone know any tricks to get this thing to run cooler, or at least to keep from going through starters every other month?
     
  2. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Buy an starter heat shield and some of that insulation stuff. I'm trying to think where I got mine because I think it was up your way. I wanna say there's a shop in Rathdrum next to the IGA. But I cannot recall the name. Anyhow it works well. You may want to also look into a remote starter set up down the road too. But try the heat shield. Worst you are out $8-10 bucks or so if it doesn't work. Then start considering the more expensive fixes on it...
     
  3. loudnowlouder

    loudnowlouder 1/2 ton status

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    you really shouldnt be running 210 all the time with the heater on, if you have a good radiator it should be fine on the highway even if the fan isnt working very well..
    you might want to check your carb (i assume its carbed since its an 85) and your timing...
    if either of those are causing it to run lean, that could be the problem with it running hot...
    you might be better off to solve the problem than to fix the consequences of it, it could be as simple as the thermostat isnt working properly, or maybe its just too high of a temp thermostat, an easy way to check is to just pull the thermostat and run it without one, see how it acts on the highway...
    but you should probably try to figure out why its running hot before putting money into shielding everything...
     
  4. mountainexplorer

    mountainexplorer 1/2 ton status

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    Yeah, its got a Q-jet on it. The 400 motor was actually out of a '76 Suburban. The radiator is out of a '77 Crew cab that had a 454. Everything is in proper tune and timing is right on.

    I just got it fired today after putting a charged battery in it, and the starter works perfect now, hot or cold. I'll check the thermostat next. Maybe the temp guage is just off. It hasnt boiled over yet, even once when the guage got up to 260 last May (the same day I fried my TH350 tranny driving on backroads). But it sure felt hot under there last night, even after sitting for an hour.
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    BINGO! You answered your own question. The 70's temp senders are bigger and have less resitance compared to the 80's senders which are smaller and give more resistance. I knew my '82 wasn't running hot, but the gauge thought I was (crate 350 with large sedner in it). Or '81 K5 with a '78 motor always did the same thing after the motor swap. I went down to Northen Autoparts (I live right by it) and told them to give the correct sender (which is to small) and all the senders you have to fit the big hole. I then just clamped an ohm meter on every one until I got a reading the matched the correct sender for my '82. The brand name is Standard and the part # is TS71.
    You may also be able to find an adapter to use the small sender in the large hole, but I think this looks better and places it more in the head to get a more accurate reading.
     

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