318 engine overheating

Heating / Cooling / AC

  1. Ricardo

    Ricardo Member

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    Hello everyone,

    Sorry if it's not the right place to ask this question

    I´m from Brazil and I have a 75 Dodge Dart with a 318 ci engine and I'm having trouble overheating. When the engine is at an average temperature, it works well, but when it gets close to 85ºC (194F) degrees it starts to lose efficiency as the engine heats and heats the holley 600 carburetor I already installed a spacer insulating between the Intake manifold and carburetor and thermostatic valve to open fully at 160ºF. The radiator has been cleaned and the coolant replaced.

    The engine is equipped with intake manifold Weiand has an internal heating done by exhaust gases, (I think is heating up too much) Has anyone already eliminated this port or know if there is any problem with the engine running if it is closed with holley carb?

    Any other idea to make the engine run a little cooler without electric fan or hard modification?

    Thank you to all !
     
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    • Demonracer

      Demonracer 71 Demon 00 Ram 16 Chrysler 300S 05 Caravan FABO Gold Member

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      Have you checked the timing, what fan does it have & does it have a fan shroud? Pictures would help.
       
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      • krazykuda

        krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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        What about your fan and shroud?

        Can you post pictures of the engine, radiator, and shroud so we can see what you have and what can improve?
         
      • pishta

        pishta I know I'm right....

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        All of Brazil is Ethanol right? Hows your jetting? Very easy to block that passage off, just get an intake gasket that has it blocked or go old school and put a piece of aluminum can there to block it and see if that helps. Not sure how long that will last but it will get you a benchmark to see if that is the issue. Usually a warm intake is a good thing. I think you may be running lean...
         
      • Ricardo

        Ricardo Member

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        Thank you to all for the answers, I will try to answer.

        The ignition is at an initial 10 degrees (instead of 7.5) due to the poor quality of Brazilian gasoline (with 27% ethanol). The distributor is original and is connected to an MSD 6AL, the spark and plugs are new. Apparently the color of the spark plug electrode does not indicate that the mixture is lean...
        About the Jets, I increased due to ethanol, currently # 69 and # 71 (secondary mechanic)

        There is a deflector on the external fan radiator fan that is original.

        I'll take some pictures and send in sequence

        Thank you.
         
      • Ricardo

        Ricardo Member

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        Below a picture of the engine 75 Dart.jpg
         
      • MOPAROFFICIAL

        MOPAROFFICIAL FABO Gold Member FABO Gold Member

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        You can block the exh cross over no problem. Just use a .020 piece of sheet metal and some high heat rtv to seal it.
         
      • toolmanmike

        toolmanmike Moderator Staff Member FABO Gold Member

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        The engine isn't overheating. You may be able to get it to run cooler with a different thermostat or larger radiator. The poor quality fuel and the carb you are using is what is causing the issue. Yes, blocking off the ports under the carb will help. Many have added a fuel filter with a fuel return port and plumbed it back to their fuel fill tube to keep the gas circulating.
         
      • Ricardo

        Ricardo Member

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        Thank you for your information, about the poor quality of fuel I understand, could you clarify more about the problem related to the Holley 600 carb. The problem is about the mechanical secondary or jets ?
         
      • tonysrt

        tonysrt FABO Gold Member FABO Gold Member

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        Is it running hot at high speed or rush hour type traffic, stop and go?
         
      • pishta

        pishta I know I'm right....

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        Idle quality good? Any hesitation on cold acceleration? I think with E17 (or whatever 17% ethanol.is called over there), you'll need to jet up 3-4 sizes from a normal 1850 jetting. A wide band o2 would help.
         
      • toolmanmike

        toolmanmike Moderator Staff Member FABO Gold Member

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        The 600's are a small carb compared to the double pumpers which have overhanging float bowls. (the overhanging fuel bowls stay cooler and help the fuel from heating and vaporizing causing rough running issues) Edelbrock carbs are effected by the heat as well. Even more so than Holleys are. The fuel bowls are in the base of the carb and directly over the hot intake manifold. Ethanol blended fuels can boil at temps as low as 130° f or less.
        You can help under hood and engine temps with a cooler thermostat if that will help and by blocking off the heat passage running through your intake. I would start there first.
         
      • Ricardo

        Ricardo Member

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        It gets really hot running in slow city traffic but don't stop and go. In high speed the temperature does not increase, but does not also decrease keeps stable at 185ºF.
         
      • Ricardo

        Ricardo Member

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        Hello, thank you for your help. I will start blocking the exhaust passage trough intake manifold and found a new thermostat.

        I also heard that there are special thermal tapes that are used in exhaust performance engines that can greatly reduce the temperature in the engine compartment

        Thank you !
         
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        • krazykuda

          krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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          Check your thermostat to make sure it opens before you install it, just put it in a pot of boiling water on your stove and make sure it's opening...
           
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          • tonysrt

            tonysrt FABO Gold Member FABO Gold Member

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            You never mentioned how you're reading temp.. Do you have a mechanical temp. gauge in the car? Can you compare with a infrared temp. gauge to make sure of Temp. being that warm?
             
          • AJ/FormS

            AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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            What elevation are you at; Brazil has a huge variation in driveable elevations. That might put a big monkey-wrench in your tuning.

            The water thermostat only sets the MINIMUM coolant temperature. It has nothing to do with the maximum.
            The maximum temp your engine might run at is governed by the efficiency of the rest of the system,and starts with the coolant itself. Water is the best coolant.
            Next up is the pump; you may need to install an anti-cavitation plate on your impeller.
            Next up is the fan, and I see you already have what looks like a 6 or 7-blade hi-efficiency all-steel fan on there. and it appears to be in a shroud. So you are good there. But IDK, it sorta looks like that fan is on backwards or it is a reverse rotation type; check it out.
            Next up is the rad; water should run out the bottom hose nearly as fast as you can pour it in the top.
            And finally is the fan clutch. IDK if you have one, and in Brazil, it might be a good idea NOT to have one. But if you have to have one, I highly recommend a thermostatic type; NOT a simple viscous type.
            Check out your fan. Here is what I run.

            images?q=tbn:ANd9GcQH5dYi-EN4fuq5llRAfnSTDGRe6BAyG6VqFQ&usqp=CAU.jpg
             
            Last edited: Jan 15, 2021
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            • toolmanmike

              toolmanmike Moderator Staff Member FABO Gold Member

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              And the boiling point of coolant.
               
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              • RustyRatRod

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

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                Check your heat riser valve in the passenger's side exhaust manifold. If it's stuck closed, it can introduce too much exhaust under the intake and cause your problem. You'll need to drop the exhaust pipe on that side and look up into the manifold outlet to see it.
                 
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                • Ricardo

                  Ricardo Member

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                  Hello, In fact, the original temperature gauge is not reliable, so I already installed a digital and an analog and both measure the same, both sensors are located on intake manifold near to the thermostat.
                   
                • Ricardo

                  Ricardo Member

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                  Hello, where I live and drive the Altitude is 850 meters.

                  The fan is correct because the photo was taken inversely, there is no clutch on the fan, the rotation is made directly by the belt so it rotates at all times.

                  Thank you!!
                   
                • AJ/FormS

                  AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                  850M is about 2788 ft, if my math is any good...

                  With 27% ethanol and a 600 DP
                  Ima thinking, your jets are too big and
                  UNLESS you have eliminated the PowerValve, the split is too small.
                  I think those carbs new, are jetted closer to 66 front, and maybe 72 out back. I'm kindof guessing here; Your altitude adjustment is about Minus 1.5 sizes , and your ethanol adjustment for 27%, might be about Plus 1.5 sizes; so the OOTB jets should have been pretty close for a 318. So yeah, at #69 your plugs should be reading rich.
                  This goes along with your engine behavior between cold and normal. A cold engine needs to be richer than a warm one. So fatjets will help the cold running, but hinder the warm running.
                  (For comparison; I run 70/72s in the front of my 367 with a 10.5PV, at 930 ft with 10% ethanol.)
                  However; running rich should actually make the chambers run cooler. And that will make it burn slower. So not all that fuel is not gonna finish burning in the chambers, and so it will have to finish in the exhaust system, and come out the tailpipes very hot. And your meager 10* Idle-Timing is only gonna make it worse.
                  Again, However; you didn't give us any clues about your 318 build, nor the combo or gearing etc, so 10* on a stocker might be just fine.
                  If you have solid lifters for instance, your power-loss during the temperature swing, could be as simple as a too-tight lash setting.

                  I think if it was mine,assuming a lo-compression engine, and about a 2200 stall; I'd start the tune at 66/74 and plug in a 10.5 PV. Then increase the Idle-Timing to 14*, and limit the Power-Timing to 34@~3400. I would modify the Vcan to ~16* and bring it in ASAP. If solid lifters, I would reset to .018 int/.023 ex. Then see how it likes it. You may have to idle it up a lil to prevent a tip-in hesitation. I would block the secondaries closed and put a few hours on it until you get the beast base-lined.

                  IMO
                  there is nothing intrinsically wrong with 27% ethanol. If I could get it around here, I would retune my combo in a heartbeat to run it.
                   
                  Last edited: Jan 16, 2021
                • Ricardo

                  Ricardo Member

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                  Hello, Thanks for the information, they are very technical and I will try to follow...
                  You're right, #69 jets in primary it´s rich, strong fuel smell exhaust at idle...I will reduce it asap...
                  The engine does not have any type of hard modification, flat pistons, 0.20" , original camshaft (hydraulic lifters) and original exhaust manifolds. Only the Carburetor and the intake manifold Weiand have been modified. Manual 4 speed transmission and 3,14 differential....Grandpa's car, (in Brazil of course) lol

                  The vacuum in the intake manifold at idle is 18, so I don't remember but i think a 8.5 - 9.. power valve is already installed.
                   
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