408 cooling issues

Heating / Cooling / AC

  1. sport74

    sport74 Well-Known Member

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    Magnum based 408
    Magnum serpentine belt system
    Aluminum heads
    Champion aluminum radiator
    Full with 50/50 antifreeze mixture
    Stainless shroud
    Dual SPAL12 fans
    185* thermostat with air bleed hole
    Fitech go EFI4 fuel injection
    Autometer temp guage with matched sending unit
    All parts except for the block are new
    Factory A/C car, but system is removed

    Engine warms up nice, and runs good, but after 5-10 minutes at temp, (190) it starts to overheat, regardless of the fans. I have allowed the controller to work automatically, I have "turned on the A/C" so the second fan will kick on, I have immediately turned on the a/c upon starting it up to try and get ahead of the game, but nothing works. This happens in traffic, going down the road, it doesn't matter.

    IMG_20161028_163725.jpg
     
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    • j par

      j par Well-hung Member

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      Take that shroud off the back and try it.
       
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      • dano

        dano Evil Handy Man

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        Is it staying at 190 or going past that and not cooling down? Is your EFI controlling all timing? Can you monitor AFR?

        My dad tried dual fans on his Coronet with a 440 and Champion radiator and it would overheat. It actually ran cooler with no fans at all than with dual 12" fans. He put a Flex fan on and has been happy ever since, but other issues can cause overheating.
         
      • sport74

        sport74 Well-Known Member

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        So yes, it is timing control via the EFI, and I don't recall having this issue prior to going fuel injected. But it didn't run that well either, so that might be why I never noticed it. I'll try removing the shroud and see
         
      • kursplat

        kursplat FABO Gold Member FABO Gold Member

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        have you gone through the big block cooling threads? a lot of good info in those. SAMPLE
        most come back to get the water pump spinning fast enough and a good fan set up
         
      • Ccas

        Ccas FABO Vendor FABO Vendor

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        If it keeps going up a lot in temp both at idle and at speed, I'd love to say it's the radiator ;) but it is not in this case.
        New motors run hot for about 500-1000 miles
        You sure the fans are pulling and not pushing?
        Timing
        make sure your thermostat is not stuck and your water pump is working properly. with the fill cap off, make sure you see fluid moving at a decent pace.
         
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        • teringer

          teringer Well-Known Member

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          like someone has already said check timing at all rpms for advancement., it looks like your fans are only cooling the area directly in front of them and the rest of rad is not getting cooled.
           
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          • superchargeddrt

            superchargeddrt Well-Known Member

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            I have almost exactly the same configuration you have. 1969 340 block .040 over and 4" Molnar crank (418). Edlebrock aluminium heads, Fitech EFI, Champion 26" aluminium with a electric fan for a Chevy HHR ($50.00 brand new from Amazon but has to be slightly modified), 190 degree high flow thermostat and an oil/trans cooler combo with a electric fan on it as well. Both fans are being controlled by the Fitech as us my timing. My car runs about 190 degrees in traffic and goes as high as 200 when running down the road. Here's a few pics. 20180421_222237-400x225.jpg 20180421_222228-400x225.jpg 20180421_222220-400x225.jpg 20180421_222218-400x225.jpg
             
          • mopowers

            mopowers Well-Known Member

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            Which high flow thermostat do you have?
             
          • superchargeddrt

            superchargeddrt Well-Known Member

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            I think it was a Robert Shaw
             
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            • sport74

              sport74 Well-Known Member

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              Thanks for the replies, mine will stay at 190 if it's early in the morning, but ~210 in the afternoon, even while going down the road. The only vehicle I have ever had that ran close to that was a Chevy, which runs notoriously hotter than everything else. Maybe I'm just being paranoid. Just hate to waste all that time and effort over something avoidable
               
            • j par

              j par Well-hung Member

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              Where's it at again on the freeway when you're doing 55- 60 with nobody in front of you on a hot day?
              Also I'd like to know the answer to that question without that deflection shield on?
               
            • sport74

              sport74 Well-Known Member

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              Around 210 degrees
               
            • Ccas

              Ccas FABO Vendor FABO Vendor

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              In rereading I took 'it doesn't matter' as the car keeps getting hotter on the highway or in traffic. If that's not the case, I'd make some different recommendations. Also, you never said which Champion unit is in there. Is it a 2, 3 or 4 row or is it the 2 row American Eagle model?
               
            • superchargeddrt

              superchargeddrt Well-Known Member

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              I also forgot to mention that I drilled a couple of holes in the shroud and installed a couple of rubber flaps that open at speed allowing more air to pass through the radiator. They were cheap to buy and came 4 in a pack. I am considering installing the other 2 just to see if I can keep it at 190° all of the time.
               
            • MOPAROFFICIAL

              MOPAROFFICIAL FABO Gold Member FABO Gold Member

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              Lose the electric fans, toss the shroud, put a pulley fan on it about an inch away from the radiator.
              I never use a shroud , never use electric fans... always problems with every customer who showed up with them and cooling issues. Uneccessary amperage load and always borderline for the size of the radiator...which is almost always too thick=too many rows! 1 or 2 is enough if they're sized right.
              i use a bmw radiator out of a 3-5 series...it's single row cross flow. 40 bucks used.. and mounts like a late model on pegs...weighs only as much as the coolant in it ....going on 16 yrs.
               
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              • BrianT

                BrianT Let's go!

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                I'm running a similar combo with the dual Champion fans and three core radiator. My 408 runs right at 210 degrees on HOT days. So does my brand new Chevy truck. I'm not worried about it.
                 
              • Willyrd

                Willyrd Well-Known Member

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                Honestly, champion radiators are kind of trash. Cold case runs circles around them
                 
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                • 512Stroker

                  512Stroker We are all here because we are not all there.

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                  If your engine gets hot all the time your cooling system is undersized. In other words your radiator does not have enough capacity to shed the heat developed by the engine. You can play all want fans and pulleys, timing etc it wont help.
                  Make sure the impeller is not slipping on the water pump shaft, had this happen on a new pump, drove me nuts for 6 months.
                   
                • Ccas

                  Ccas FABO Vendor FABO Vendor

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                  This will help on the highway only. It could cause some increased temps in traffic if they don't seal just right.
                   
                • Ccas

                  Ccas FABO Vendor FABO Vendor

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                  If it is the Champion 2 or 3 row or the American eagle 2 row, You can lower your highway temps by 10-20 degrees by adding more volume to the system. ie a bigger volume radiator.
                   
                • superchargeddrt

                  superchargeddrt Well-Known Member

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                  Mine seal perfectly. They were made with flexible nubs on them that allow them to move freely.
                   
                • Ccas

                  Ccas FABO Vendor FABO Vendor

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                  good. Just keep an eye on them. Over time, the rubber can get harder and not seal as nice. At that point you can just replace them with new flaps.
                   
                • gtsdude

                  gtsdude Well-Known Member

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                  I have the HHR fan on a summit 26x19 universal 2 row aluminum radiator and a gutted t stat, the fan pulls a lot of air. The problem I had was on the highway my temps would creep up and with no hood scoop under hood temps went up and the fuel would boil in the carb. I did cover my steel lines with foam wrapped in metal foil tape and installed an aluminum plate under the carb to help with the fuel boiling. I picked up a 7 blade clutch fan, no shroud, just to see how that would cool it. I now need a thermostat, I have only driven it a few times but the temp stays around 160 or so. On my car I think the small opening of the fan on the shroud and the fan blades block a lot of air flow going down the highway.
                   
                • famous bob

                  famous bob mopar misfit

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                  The reason it heats up on the road is the thin shroud . Been there done that !
                  Or an unsealed carb to scoop pan.
                   
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