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Fresh rebuilt motor seems to run HOT!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Timmer_71, Aug 29, 2002.

  1. Timmer_71

    Timmer_71 Registered Member

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    I just rebuilt my 350 and fired it up for the first time tonight but I had to shut it down after about 4 or 5 minutes because the headers at the number 1 and 2 cylinders started to glow a dull red and then seemed to almost turn orange. I dont know if this is normal or not because I never really paid attention and it was in the dark in my driveway at about 10 o'clock pm. I do not have a temperature guage hooked up and I do not know if the timing is quite right either.
    One possibility I overlooked was that the thermostat was sitting in the intake for about 3 years on the shelf in my garage, maby it is frozen shut? I did notice that the upper radiator hose would swell up a little at the intake when I reved the motor up. This gives me the impression that the water pump is working. Something else I did though was take a water pump from an '86 305 and bolt it to my '71 350. I just assumed that it would line up. Could this cause a problem?
    Could the timing cause it to run hot?
    Or am I just being over cautious, because the motor sounded nice and quiet (no ticking, grinding or anything like that.)
     
  2. 90K5

    90K5 1/2 ton status

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    Sounds like the thermostat is stuck.
     
  3. Supergas

    Supergas 1/2 ton status

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    Make sure that you "Burp" the engine.. Have the water inlet on the radiator higher than the engine and fill it.. then turn on the water pump, or start the engine and let it cycle the water, then top it off. You may have to do this several times.. What this does is remove air trapped on the back sides of each cylinder.. Make sure you have a NEW thermostat in the engine. The worst thing you can do to a new engine is start & stop it prior to a full warm up cycle... Not more than 50/50 mix of water & antifreeze & you might add some "water wetter" to help it out...
     
  4. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    Sounds like a timing issue, or real lean mixture. Check the temp gauge. If the temp gauge reads normal, but he exhaust glows (especially at idle) I would almost bet it's a timing issue. If the motor runs, unplug the vacuum advance to the distributor (remember to plug the vacuum line with something) and set the timing at idle.
    Hope this helps.
     
  5. Timmer_71

    Timmer_71 Registered Member

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    Thanks for the responce guys,
    I am going to pick up a new thermostat on the way home from work today and install it as soon as I get home, then I'll top off the water. Should I just leave the radiator cap off for the first minute or so while I try to add more water/antifreeze?

    Also, I am pretty sure the timing is not quite right, I have not had a chance to check it with a timing light, (I just got it started) I only had a chance to turn the distributer by hand, starting with it set "retarded" and turning it more "advanced" until it started to run "ok".
    But I am still wondering If it is normal for headers to glow at all when it is dark outside?
     
  6. sosamantx

    sosamantx 1/2 ton status

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    it sounds like timing or running to rich to me? also, if you do replace the thermostat, you can drill 2 small holes (on the outer ring of the thermostat) and you should never have the problem of having air in the system. and no, the headers should not glow (even at night).
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    I agree. If the motor itself was running hot, you'd have steam make its way out of every fitting on the block before you started turning metal red.

    Timing or mixture is likely the cause. You may cover up the problem a bit if the t-stat is sticky and you replace it, but I really don't believe (only) a couple of exhaust runners will glow just because the block is hot.
     
  8. Timmer_71

    Timmer_71 Registered Member

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    Well, I put in a new thermostat, I also noticed that the water was about 4 or 5 inches too low in the radiator, so I filled that up, advanced the timing quite a bit and now it run's great. Thanks for the suggestions guys.
     

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