Overheating

Discussion in 'Engine Topic' started by Scott Sievers, Jun 5, 2020.

  1. Scott Sievers

    Scott Sievers Veteran Member

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    With the AC on the temp goes up steadily, no matter if it is idling or going down the highway.

    Lower hose is new and has the spring in it. I will check on the Radiator and put my scope down in it to check the tubes when I swap out engines. The 4 row is supposed to handle a lot of HP, and the 434 is going to be capable of a lot of HP... Both the fellow I ordered the cam from and the people I got the engine from, it should be 1000HP+ with the nitrous. I am not that optimistic, and if it is that stout I will probably not even fill the nitrous bottle.. just leave it in there for show!
     
  2. dcozzi

    dcozzi Veteran Member

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    Maybe a steam pocket in the thermostat housing? Have you tried to use the idiot light port in the block for the sensor. I know that sucks because the line never reaches but you could also put a separate gauge inside the engine compartment and see if it reads the same as the one in car.

    EDIT: But, that would not explain anything if the car is fine without the A/C on. Crap, I'm stumped.
     
    Last edited: Jun 10, 2020
  3. Scott Sievers

    Scott Sievers Veteran Member

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    I always drill a 1/8 inch hole in the flange of the thermostat so that it self bleeds, so i am pretty sure there is no air in the system. Most of the parts I need to finish assembling the 434 should be here this coming week. When I take it apart, I will go through everything with a fine toothed comb, and see if I can SPOT anything amiss.
     
  4. cnlmustard

    cnlmustard Member

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    I have a 79, warmed over 400CID. Everything I've read here is identical to what I tried (except the electric fans which are in the way of airflow, and cant compare to the monster OEM fan blade). Checking it with remote air probes, I could see that the air flow pattern at high speed on this car, causes the road air to actually recirculate around the radiator. Anything over 50, and I had to turn the heat on full blast and open the windows, to get where I was going. It steadily got worse (big clue). I did change the thermostatic fan clutch with a used one I had. No difference. 4-core rad, 160 stat, and even tried blocking off openings under plastic bumper to stop recirc.
    After about 5 years of this, I just happened to notice on an extra hot day, that the fan just didn't seem noisy under the hood like it gets sometimes. I tied a thin twine string to one fan blade to hold it, started it and the blade didn't spin. When the guage was up in the red, and it still held, you KNOW that clutch is bad. When it blows full speed you should hear the fan air 50 feet away on that sucker, after idling a while!
    If you haven't tried it yet, get a BRAND NEW fan clutch in there! It popped that little string test in about five minutes after cold start, and runs a nice 160 degrees, at ANY speed, A/C on full blast, problem SOLVED. These clutches seem to have a limited life, the used one was obviously already bad, but that hadn't occurred to me. Make sure you have the one with external bimetal sensor. Replace the shroud you cut up, it needs that close fit. (I'm an HVAC tech and Professor, if anyone want's to debate this.) Don't put anything in the airflow path that isn't factory. I read in a design guide, that at full tilt that fan drags about 5 HP off the engine. That equals a 3,700W electric fan, which would draw 310Amps! Electric fans are for dinky 4-bangers, and not a blown V-8.
     
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  5. Scott Sievers

    Scott Sievers Veteran Member

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    Hey cnlmustard... funny you should mention all of that... After working on the 434 yesterday.. I pulled the shroud and fans off the new aluminum radiator, and put a stock fan with a new fan clutch from my 89 truck. Obviosly with the blower the shroud would not work.. but, for this test I wanted to see what was happening running down the highway... 86 degrees, nice day... headed out on the highway, cranked the AC up to wow, and just drove. After about 30 - 40 minutes, it was running just over 200 again.... so I shut off the AC and turned around... It cooled down to about 185ish for the drive home with the windows down and no AC running.. I do think I am going to do away with the electric fans and try to run a clutch or flex fan. I will have to get a new shroud that I can modify to clear the blower/belt etc, once I set the 434 down into the car. My next test will be checking JUST how ungodly hot that AC Condenser is getting, and see if I can figure out something from there...

    DSCF5267.JPG
     
  6. xten

    xten Veteran Member

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    OOOH ^^^^ That's purdy!
     
  7. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Guess I'm wondering why I bought a GM electric fan setup from a mid 90's LS 1. Don't think any LS engine, or mine, is a dinky 4-banger.
     
  8. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    Yes it is, my wallet started screeching. :D
     
  9. rburrow87

    rburrow87 Veteran Member

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    Yeah it's not 1940, electric fans have come a long way. And it's not like this is a 15L semi truck diesel engine running at full tilt at max load all the time. It's a small block v8 cruising on the highway only making maybe 35hp to maintain speed. And in this case, just idling. It really should not need 3.7 kilowatts worth of fan under such conditions, AC on or not. Either something is jacked in the engine or the radiator ain't radiating very well. Too many people are running around with a $100 1-row parts store LT1/LS1 4th gen radiators and 4th gen electric fans from the 90's (myself included) with no issues.

    That is a beaut!
     
  10. Scott Sievers

    Scott Sievers Veteran Member

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    running down the highway it shouldn't even need fans, so yeah, something is definitely messed up. When the big mouse goes in, everything will be torn apart and gone through in meticulous detail. I'll fix it, come hell or high water!
     
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