Bob's Component Restoration, Part 23: Thermal Control

Members Restorations

  1. cruiser

    cruiser Well-Known Member

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    Good evening kiddies! Rumor has it that some of our brother/sister Moparites are having trouble of late falling asleep without a slumber inducing story from yours truly. And so we present tonight's latest chapter to help you drift off: Thermal control. Every single one of us has a liquid cooling system in our Mopar rides. And yes, you can run your motor without a cooling system (like a VW Beetle) if you don't mind your engine seizing up into a solid mass of iron. I don't recommend this. Thermal control is critical to a liquid cooled engine for this reason, so tonight we cover how I've renewed the entire system in my slant six powered 1974 Duster. As you probably know, only about 25% of the gasoline's energy in an older car is actually converted into power at the rear wheels. The rest is given off as waste heat through the cooling system and through the components themselves, such as the rear differential. My cooling system was a mess when I bought my Duster in 2019, so here's how I converted it into a reliable system that wouldn't fail me on the road. I knew that I'd have to clean out the block as best as I could by backflushing the system with a chemical solution. I began by replacing all heater and radiator hoses and installing a backflushing tee into the 1/2" heater inlet hose. I also rebuilt the heater and replaced the heater core. The replacement core was a lovely little unit with copper and brass inlet and outlet tubes (see photos). I also got rid of the incorrect aftermarket radiator and installed a rebuilt correct part number radiator in its place, along with an NOS 1974 model year only radiator cap. The new radiator's core had more cooling fins than the original, but was still a two row core to keep the original look. I also replaced the water pump and coolant temperature sensor at that time. See the photo of the new and old pumps alongside one another. Now that I renewed all the major components of the cooling system, it was now time for the chemical backflush, which yielded a huge flow of crud from the block. Eventually, clear water ran out which meant that the cooling jacket was about as clean as it was going to get. I then installed 6 1/2 quarts of Prestone II antifreeze to create the correct 50/50 coolant mixture. After running it for awhile, I was unhappy with the performance of the thermostat, so it was time to replace it with a new Stant 195 degree Super Stat. The stat that NAPA sells as a Super Stat looks different than the older ones that you can buy on e-Bay. The old ones have a nice brass core that the new ones don't have (see photos). So I went with the old one and I'm glad I did. When I reinstalled the factory original thermostat housing, the bottom flange cracked and began leaking, even though it was torqued to factory specs. I bought a new housing and have included a side by side photo of both. The old one was a seriously pitted iron casting and the new one was cast aluminum. I think the old housing had too many removal and installation cycles on it and simply cracked due to its age. I've included a photo of the new housing on the motor. So when you think about it, there is now nothing left to renew or replace. The result is a reliable system that cooled beautifully during my recent 4540 mile eleven day road trip through the south. A few random observations: First, the aluminum versus copper radiator debate rages as always, but I cannot tell a darn bit of difference between the two of them. They both cool just fine. Yes, aluminum is lighter but I'm not looking for lighter. I'm looking for a vintage look. Copper and brass radiators have worked wonderfully for well over a century, especially when they're well maintained. Second, I didn't want to monkey around with the heat range of my stat. I figure Ma Mopar had a pretty good reason for going with 195 degrees back then and I'm not inclined to go against this. Third, a frequently overlooked component of this system is the transmission cooler in the bottom of the radiator. These are prone to leakage, so I had my radiator guy check it over before he re-soldered it into the bottom tank. Mine works great and keeps that slippery red tranny juice nice and cool in the torque convertor. Make sure to inspect yours carefully when you rebuild your radiator. So there you have it. An effective and reliable cooling system that delivers all that nasty excess heat to the atmosphere and keeps your motor warm and happy. So please picture this as the bottom line of tonight's story: Its a beautiful late November day as you head north into the cold northern forest of Minnesota (my home state). 40 degrees in the garage, 25 outside. The Duster starts right up on the first flick of the starter, settling into a nice high idle. Warm her up for a minute, then kick it down to a curb idle and you're off onto the deserted highway. Coolant temperature comes right up to 195 degrees as the 48 year old radiator and thermostat do their job. Heater keeps my toes toasty warm, engine purring like it was built yesterday. Such a lovely view outside: trees, fields, lakes and rivers. The Torqueflite tranny running flawlessly, dumping all its waste heat into the cooler in the radiator. A big smile on my face, no need to listen to music because I'm listening to motor music. This is the payoff for all the hard work, skinned knuckles and trips to the parts store. Now keep this image in mind as you turn off the light and climb under the covers. Night-night!

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    Last edited: Nov 27, 2021
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    • GGs66GT

      GGs66GT FABO Gold Member FABO Gold Member

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      Great story , gorgeous Duster !

      yawn … smack …smack … yawn … yawn. Nite nite .
       
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      • cruiser

        cruiser Well-Known Member

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        Yay! It worked!
         
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        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          That's gotta be the nicest slant 6 Duster ever. You've done a great job on it.
           
        • cruiser

          cruiser Well-Known Member

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          Thanks, Rusty!
           
        • GGs66GT

          GGs66GT FABO Gold Member FABO Gold Member

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          Yawn … Good morning ! I had a great nights sleep ! Tell me another story … ppplease .
           
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          • 4spdragtop

            4spdragtop CONGRATS NORTH AMERICA! FABO Gold Member

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            Attention to detail is amazing!:thumbsup:
             
          • Mtrhead

            Mtrhead Ace of Spades ♠️

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            Bob you should run a "high end" detail shop...replating,buff,resprayed,interior,elec....etc....it takes the passion you have ..and patience..
             
          • cruiser

            cruiser Well-Known Member

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            Yeah, I guess I missed my calling!
             
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            • cruiser

              cruiser Well-Known Member

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              Ask and you shall receive. I just posted my latest component resto chapter 24 dedicated to you. Check it out!
               
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