Heat soak vs fuel pressure

Fuel and Air Systems

  1. MWFan

    MWFan Well-Known Member

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    So I went to the local cruise in in Elizabethton Tn yesterday, the car (440 basically stock Magnum replica) ran flawlessly until I went down and got a big barbecue sammich and came back to angle park it and open the hood. Didnt want to start, had to floor the pedal, tried to clean it out, black smoke ran rough and when I got the hood open it was hot as a 2 bit pistol. It is an Eddy 600 and I read here how vulnerable they are to heat soak. I'm betting on a phenolic spacer helping this, but reading about high fuel pressure problems causing the same issue. My common sense (?) says if it was fuel pressure it would happen cold or hot, no?

    Thx, Bernie
     
  2. HT413

    HT413 Semi Pro Bowler

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    Yeah I think you’re right, high fuel pressure would be all the time. sounds like heat soak to me.

    Small spacer might help but you may end up with clearance issues depending on your setup. Might try adding a return regulator and return line. It’ll solve any over pressure issues while it delivers cool fuel, helping to minimize the heat soak.
     
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    • moparnation74

      moparnation74 Well-Known Member

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      Sounds as heat soak to me as well....
       
    • snakeoil24

      snakeoil24 FBBO Gold Member FBBO Gold Member

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      Do you have a return line to the tank?
       
    • Dennis H

      Dennis H FBBO Gold Member FBBO Gold Member

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      How long was the engine off. Spacer may help but don’t expect miracles. Ethanol evaporates at 170 ish. Only cure is EFI. This problem only seems new/worse now because of todays fuel.
       
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      • ckessel

        ckessel Well-Known Member

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        Heat soak baby!. Pull the intake off and replace the valley pan with a unit that has the exhaust crossover blocked. From there, put an insulator between the carb and manifold. When I worked at the speed shop years ago, we sold the GM [ewwww] units by the bucket load. They were the bomb especially in an RV as that doghouse is tight and cooling airflow is minimal across the engine. Standard flange carb, yours or other 4150 style, can use the 3969835 GM unit which is reproduced by Classic for Camaro [more yuck] under that number. From there, make sure your fuel lines are as far away from heat sources as possible. Like Dennis said, the ethanol laced fuel has a boiling point thats less than what the engine runs at. If its boiling 150-170*, your engine is 180 or more, hot air from the manifolds/headers etc, you will have a tough time getting it under control. Might be time for some EFI.
         
      • MWFan

        MWFan Well-Known Member

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        Nope
         
      • snakeoil24

        snakeoil24 FBBO Gold Member FBBO Gold Member

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        Return line andwhatscsaid above will help plus insulate the fuel line in the engine compartment
         
      • Lionized

        Lionized Well-Known Member

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      • Dennis H

        Dennis H FBBO Gold Member FBBO Gold Member

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        Did the 1/2 spacer, wrapped and moved fuel lines, evrything worked and still could not overcome the heat soak restart. Engine temp never got over 195 even at 100 in Vegas. Gave up and put Pro Flo 4 on. Ethanol low boiling point cannot be overcome. Bowl will be empty after a lunch stop. 5 times to the floor, Black chunks, smoke and noise then ok til the next stop. Gets old.
         
      • ckessel

        ckessel Well-Known Member

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        I even had the fuel in the tank boiling after having the car out for almost an hour. Tank was 1& 1/2" or so from exhaust.
         
      • R/T

        R/T Well-Known Member

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      • miller

        miller Well-Known Member

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        Questions are...what intake manifold? Iron, or aluminum? Crossover blocked? If not, it needs to be.
        What fuel pump? Mopar motors don't like much more than 5-7 lbs.

        Won't get into my set-up, unless you want it, but doesn't seem I have any issues with mine. At most, a couple pumps on the pedal, if it sits too long hot. Twin 600 Eddys, aluminum intake, crossover blocked, and only so-called Eddy insulated base gaskets. Most of the time, fires right off, turn of the key.
         
      • Lionized

        Lionized Well-Known Member

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        Are you running a return line?
         
      • lewtot184

        lewtot184 Well-Known Member

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        I use the factory return/vapor separator with one of those black edelbrock insulator gaskets on a stock 440. this thing runs hot all the time but I never have starting issues because of heat. the return relieves the pressure on the carb and the insulator gasket seems to provide enough protection to prevent boil over.
         
      • MWFan

        MWFan Well-Known Member

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        Thanks all. I have gotten this issue fixed, but the phenolic spacer didnt do it. I put it on and left it on but only because I thought it did run a little stronger.
        I did some more reading regarding overheating and became convinced that the solution was a well sealed fan shroud. The car didnt have one when I bought it but did have a Flexolite electric fan. I found a shroud for the car but it didnt appear to be well sealed and would have been pushing $400 by the time it got shipped. I have hobbied with old school fiberglass speedboats for years so I made one out of fiberglass. I sealed all edges of the radiator to shroud joint with a firm foam insulation. It has not overheated or had hot start issues ever since. I removed the electric fan.
        Thanks.
        Bernie
         
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        • JackpotJim

          JackpotJim Well-Known Member

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          I had same issue on my Coronet. Fuel pressure would drop to less then 2 lbs from 6.5 lbs after a half hour of cruising in 80 degree heat. gas was basically boiling in my fuel lines on top of the motor. I ended up wrapping my fuel lines in the silver insulated wrap that is available from Summit. 66203797_2487737977905563_5881337681803214848_n.jpg Have not had a issue since.
           
        • Ranger16

          Ranger16 Well-Known Member

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          [​IMG] I'm a bit confused about this. If this is the case, shouldn't our fuel be boiling all the time and stalling out?

          When I first got my car (383, Edelbrock Performer RPM manifold w/valley pan and an Edelbrock 750), I could hear the fuel percolating in the bowls when I shut down. I pulled the factory recommended 190° thermostat and swapped it for a 180° and added a fan shroud and never had that problem again.

          I took her for a ride today. It was close to 90° and I got caught in some construction traffic for a good :20 min.. Temp went up to about 195°, but the engine never skipped a beat. Shouldn't I have had problems?

          Same situation before I swapped the stat and added the shroud, but that time it reached 230° and still never vapor locked. What am I not understanding?
           
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          • Kern Dog

            Kern Dog FBBO Gold Member FBBO Gold Member

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            I have not had that problem and I had the same carburetor as you. Yeah, the fuel does evaporate faster but what really helps is to keep the fuel in a "loop" as is done with most fuel injection systems. I run my 3/8" line to a regulator with a 1/4" return line to the tank. I have no hot start problems.
             
          • MWFan

            MWFan Well-Known Member

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            I am no expert but I believe there is more to a well sealed fan shroud than just how well it cools the liquid in the radiator. I had checked airflow by putting my hand in front of the radiator (with just a stainless flex fan) before I put the shroud on and outside of the actual fan area there was very little air movement. Once the shroud was installed, there is strong air movement everywhere except at the center of the fan. I belive that part of the shrouds job is to evavuate the underhood air efficiently so that even if the engine is running at high temperatures that cooler air is running through the engine compartment allowing external components to be cooler than the coolant. I know there was very little air going in to the engine compartment without the shroud. Even at the far edges of the radiator, with the shoud l
            could feel strong air movement.
            Thant my non scientific two cents worth...
            Bernie
             
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