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How hot is hot??

Discussion in 'The Garage' started by highlow, Feb 11, 2005.

  1. highlow

    highlow 1/2 ton status

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    How hot is too hot on an engine. I am curious what you guys are seeing out on the trail while you are wheeling at slow speeds. Arizona guys I really want to hear from you guys. Right now the blazer has a zirgo electric fan a 16" and it is one of their higher cfm units I can't remember. Any ways no shroud right now mainly cause the blazer did not come with one:D I am probably going to shroud it though I think it will help. Right now it is overcast and rainy and just putting the blazer around I get up to 180 on the temp gauge whats it gonna be when it gets up to 110+ in the summer time??


    EAT AMERICAN BEEF
     
  2. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I have a stock fan and HD clutch , replacement water pump ( I had a modded impeller one that died ) , and 50/50 mix . I see 185 almost all the time , 195-200 with a/c on at idle in 110 degree days :D
     
  3. sled_dog

    sled_dog 1 ton status

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    you understand the function of a thermostat? In theory it should sit at 180 365 days a year. 180 is very close to optimum temperature for most motors. Mine runs up to 210, 220 sometimes. I have really bad cooling system. Don't worry about it till it is actually an issue.
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    My built 406 runs about 200* all the time on my mechanical guage. Thats with a new 4 core, dual 13.5" electric fans, hi flow water pump, and a 180* stat. I have no problems at slow speeds but under heavy throttle it will start to slowly climb if I stay in it, like pulling on something or a load over a hill.
     
  5. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Your engine should, ideally, stay at whatever temp the thermostat is. If you have a 180 deg stat your engine should stay there whether its hot or cold outside. If the engine is pulling really hard (more friction=heat), the radiator is not flowing to full potential or the outdoor temp is so extreme (over 100 deg) and you dont have much airflow through your rad you might see engine temps rise. Anything over 205 is unexceptable. My old Jimmy has a solid fan and 4 core rad and never overheats crawling all day long in the summer, my gauge doesnt have number designations but Im guessing its at 180 normally and spikes to 190 or so when really worked.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    GM has no problem running their engines up to 220* (mainly for emissions as I understand it) however, as others have said, as long as the cooling system is up to the task, thermostat temp is where it should sit. Secondary GM fan on TPI apps came on at 240* FYI, and there is nothing special about the motor construction on those engines that would prevent an older block from running that hot either. Not that I'm suggesting 240* for a normal high end, just that the engine SHOULD survive running that hot for a short period.

    Electric fans add another dimension though, since there is an on/off threshold, you can either cycle the fan constantly (or always on) trying to keep rated t-stat temp, or have it come on high and turn off above t-stat rated temp, which is what GM did.
     
  7. goldwing2000

    goldwing2000 Guest

    A lot of it also depends on where your temperature sending unit is located. Ideally, it should be right at the water outlet, so you're getting an accurate indication of the water temp at the thermostat. Unfortunately, most small blocks have the sender on the lower left side of the block. This can cause temperature fluctuations based on water flow rates.
     
  8. darkshadow

    darkshadow 1 ton status

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    i have always knowen 180 as the best temp.

    yeah you can run it at 250, i had to once and dident wreck anything after 15 min of driveing, but it is not the right way!!!


    you want 180, if its cold block the rad ( not the bottom 2")

    if its hot need more cooling,
    summit has this cheap looking plastic fan that is only 15 bucks or so, it is so light , and the blades are at 90* it cools like nobodys busness!!

    it is a nice cheap fan that really works!!!!!!!
     
  9. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I agree , and I moved mine off the head , to the water neck where a ported switch used to reside . 70's single hole waterneck worked for me , same thread as 83 sender :k5: :k5:
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    If you don't verify the gauges accuracy (stock gauge or not) then sending unit location REALLY doesn't matter, as long as the gauge moves to indicate coolant temp. Pay attention to what the "normal" range is, when the reading exceeds normal, you have a problem. Just like an oil pressure gauge...if it normally reads 30PSI at idle, and all of a sudden reads 0, you have a problem. Doesn't matter if 0 is ACTUALLY 5PSI, something has gone wrong, and the gauge is just relative.

    My stock gauge, fed out of the drivers side head, reads pretty close to what the ECM sender in the intake says. If the gauge starts going hot, I know I've got a problem.

    Coolant flow rate is ALWAYS going to depend on engine RPM and whether the t-stat is open or not.

    I too have heard that 180* has been shown to be the best for power production. Keeping a vehicle at 180* in all conditions is very hard from what I've seen, ESPECIALLY when crawling in hot weather with one of these trucks.

    Even below 32*, slowly going uphill or idling my truck will hit 220*. It goes that high due to the electric fan coming on at that temp, but the temp increase itself is due to airflow over the radiator being almost nonexistent based on speed.
     
  11. MarcS

    MarcS 1/2 ton status

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    I agree, as long as you know your "normal" range, the sending unit location doesnt really matter. Just matters if the temp goes up :eek:

    Another thing is the pressure cap on the radiator. Under pressure, the temp can go over boiling point with no problems.
     
  12. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    If a 2nd gen truck is routinely seeing temps above 205 deg with a 180 deg stat there is a problem. An engine running routinely at 220 deg is too hot for me. In a high compression race motor its not unusal but the typical stock engine with as good as new radiator, heater core, fan, shroud, 180 deg stat and 50/50 coolant mixture you should see temps much lower unless there is a bad head gasket. Remember we are talking about what he can expect in his truck, not TPI car.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    There really isn't much point in arguing this. You say 205* is too hot with a 180 stat. (and the title of the thread IS "How hot is too hot?") I can just as easily say that if you can't keep it at 180*, your cooling system is inadequate, and that is just as true. 205* is an arbitrary number you selected, not the result of some study or calculation.

    Why does the induction system have anything to do with how hot GM thinks a 350 engine can run without harming anything? GM picked those numbers KNOWING they had to warranty those engines for so many years.

    You say running "routinely" at 220*. Just to clarify, running "routinely" at that temp IS a problem. With my 195* t-stat, if I'm cruising down the road and can't maintain rated stat temp, there is a problem. If I had a 180 stat, I'd expect that temp to be constant. What I'm saying is that it is NOT a problem to the engine to run between say 195 and 220* under heavy load or idling. You remove the fan from the system, the stat doesn't make a bit of difference as to whether the engine stays cool while idling or crawling.

    With a clutch fan you don't notice the "cycling" as much as you would with an electric, thus one of the reasons electric fan on/off temps vary by so many degrees, which you don't see with a clutch fan or flex fan.

    No matter what temp stat I was running, if I couldn't keep it at that temp on the freeway, I'd know there was a problem with the cooling system, and the stat has no bearing on that, unless the cooling system is inadequate and unable to keep the coolant temp down.

    These 220* temps I'm talking about are in my truck, with a new 3 core radiator, new 195* stat, new engine, new water pump, and new radiator cap, so it is entirely relevant to what anyone can expect. I'd put my "hot running" engine up against any other and the least of the worries in regards to power would be coolant temp. Regardless of induction system, a 350 engine idling or crawling in a 2nd gen truck generates a fair amount of heat.
     
  14. Hossbaby50

    Hossbaby50 3/4 ton status

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    With the carb I ran between 200-215 most of the time. 220 came around sometimes if I was climbing steep grades or something. With my FI system in I sit right at 195 most all the time. Sometimes it will run up to 205-210 if I am romping on it.

    Harley
     

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