What should be my temp?

Small Block Mopar Engine

  1. tony20110

    tony20110 Well-Known Member

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    I have a 1973 360la in a 66 cuda. Bored .30 and zero decked. Stock crank, KB pistons, comp high energy 268 cam, ported polished heads, air gap with a 2 inch riser, holley 750, hedman fenderwall headers. 9.5-1 compression. I have a 22 inch champion radiator with dual fans. I'm guessing I'm around 385hp. I idle in park at 1100 rpm and in drive at 900-800. What should be my max temp? Thanks in advance.
     
  2. mopowers

    mopowers Well-Known Member

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    Anything over 230 makes me pucker.

    Why such a high idle and large rpm drop in gear?
     
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    • tony20110

      tony20110 Well-Known Member

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      The cam
       
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      • Mike 340

        Mike 340 Well-Known Member

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        I have the same cam. Idle in park is 850rpm and in gear 750 rpm. Sounds like you have timing or carb issues or both.
         
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        • SIX225

          SIX225 Well-Known Member

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          What are you using for a temp gauge? The one in my dash reads a lot hotter than it should, yet an infrared temperature gauge reads closer to normal. I've tried several different senders but no change. Might be worth looking into.
           
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          • Yote

            Yote Well-Known Member

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            Your temperature should be close to what your thermostat rating is unless the ambient temperature is extra hot or after a hard run.
            Yote
             
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            • AJ/FormS

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

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              The stat sets the minimum coolant temperature. The rest of the cooling system, sets the maximum temp. If the fans cannot pull enough air through the rad at idle then the temp will rise and rise and rise and then the rad cap will finally blow off, releasing the pressure, and then it starts all over.
              This does not usually happen over 30mph, cuz ram air thru the rad is usually sufficient to help the rad shed heat.
              Of course the pump has to be able to move the cooled water thru the engine.

              If you are asking what is a desirable minimum water temp to run, I think 205*F is a good number. Engines can and will make more power at a lower temp , but they will also wear out faster at that lower temp. Some say 195*or 185* is a reasonable compromise. My philosophy is that if you can spin the tires all the way thru first gear, you already have more power than the chassis can handle, so, how about giving up some power for long life. I have been running 205 since 1999 AND blowing the tires off to well past 50 or 60 mph.I call that a good compromise.
              I run fresh cold air into the carb.
              If your engine is sucking in hot underhood air, you may have to run a lower minimum temp to keep the engine out of detonation. Avoiding detonation is priority one.
              A high idle rpm creates a lot of underhood heat.You really need to get that lowered. I run a 276/286/110 cam, and my idle is 750 or less. It is a stick car, and I can pull the idle down to 650 or less with the clutch.I only idle it at 750 to ensure lots of oil is circulating.I'm not impressed with a lumpy idle.
              If you haven't already set the T-port sync, this should be at the top of your to-do list.
               
              Last edited: Apr 28, 2017
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              • mopowers

                mopowers Well-Known Member

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                There's no reason that baby cam should need to idle so high. Give that thing more initial timing and work on the tune. That has a definite effect on running temp.
                 
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                • fishy68

                  fishy68 Tyr Fryr's Inc.

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                  I run mine at 190* as it's more efficient there. Keeps the plugs cleaner and better fuel mileage (its' a 408 so I need all the fuel mileage I can get). I'd check with an infrared temp gun as SIX225 recommended. I installed an expensive Autometer temp gauge and right off the bat it was off 15 degrees. I never trust gauges until I verify them with my temp gun

                  I know this isn't related to your question but something isn't right cause that cam should idle decent at 700-750 in neutral. Did you recurve the distributor to give it more initial timing? If not you need to
                   
                • mopowers

                  mopowers Well-Known Member

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                  What thermostat do you use?
                   
                • nm9stheham

                  nm9stheham Well-Known Member

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                  From my sons' 340 experience with a very similar setup in a '65 Cuda, the OP's 22" rad and whole cooling setup is marginal and the temps will climb. I'm gonna put in a different rad (as the Champion's 3 row design tends to be marginal), and we will work on more airflow through the whole engine compartment. With the small engine compartment and the higher temps generated with higher CR's, the heat takes more airflow in and out to control. The openings for the headers may help the OP.
                   
                • fishy68

                  fishy68 Tyr Fryr's Inc.

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                  Mr. Gasket high flow
                   
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                  • mopowers

                    mopowers Well-Known Member

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                    Does Mr. Gasket make a 190* thermostat? The only ones I see are 180 and 195.
                     
                  • fishy68

                    fishy68 Tyr Fryr's Inc.

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                    Maybe it is 195. It was 2011 when I put it in and my memory isn't perfect. With whatever is in it the temp runs 190-195 (verified by a good quality infrared temp gun). If I get in bad traffic for a long time it has crept up to 210. Never saw it above 210
                     
                  • TrailBeast

                    TrailBeast AKA Mopars4us on Youtube

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                    Yep, I run a 195 and average between 190 and 210.
                    Fans come on at 210 and go off at 195.
                     
                  • Yote

                    Yote Well-Known Member

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                    If a thermostat has too high of opening temperature the coolant can circulate too fast not being allowed to cool in the radiator. The thermostat is constantly opening and closing regulating the temperature of the coolant. Therefore if you have a 195' thermostat the temperature will probably not get below that temperature. Like wise if the rating is too high the coolant will have to get to that temperature before it opens allowing flow to the radiator.
                    I had an engine once that constantly heated from the time it was new. Went to replace the thermostat and found it had none from the factory. Installed the correct thermostat and it never heated again.
                    Yote
                     
                  • KnuckleDuster

                    KnuckleDuster Well-Known Member

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                    My .040 over 360 stroker runs 207° no matter what the weather is doing, idling in traffic or at WOT...


                    BTW, my Comp XE285HL idles about 850rpm in park and just under 800 in gear. You shouldn't have a 200rpm drop, and 1100 is pretty high. Even with the choke on fast idle mine is only at 975rpm.
                     
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