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Thread: SBC 350 overheating... need input

  1. #1

    SBC 350 overheating... need input

    This is in regards to my 25th Countach replica that just found the road a couple of days ago.

    Here are some vital stats:

    Engine: 350 cubic inch Chev crate engine
    Rad: 4 core aluminum, grill area approximately 20"x15"
    Pump: Moroso electric
    Fan: 12V, 10A, 14" diameter

    I have a homebuilt shroud over the rad. I have built a large air scoop under the car to collect air and force it through the radiator while at speed. I also have a reverse hood scoop cut in the hood, just above the fan. I am currently running NO thrermostat.

    I posted a bit of my first problem in my "Maiden Voyage" thread. I took her out today again after removing the t'stat, and adding the air dam underneath. She took longer to heat up, definitely, however she still climbed to 230 before I got her home and parked her. I'd guess that that was maybe seven minutes or so, with some good-sized hills in there to climb.

    Tonight, with Felix's help, I'm going to really burp the system hard, perhaps disconnecting the front upper rad hose to make sure that that high point isn't the culprit.

    I'm really open to any other suggestions, though. Surely the rad that I have is sufficient to cool the engine?
    Meddle not with the affairs of the Dragon, for you are crunchy... and taste good with ketchup.<br />http://www.rc-sub.com/resources/grap...ni/avatar2.jpg

  2. #2
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    Re: SBC 350 overheating... need input

    There have been numerous discussions about this problem elsewhere -research them
    That been said experience says..

    1) You must run a thermostat
    2) Lose the electric pump

    Hope this helps


  3. #3

    Re: SBC 350 overheating... need input

    I would add second rad just like the one you have. that little rad is way under sized for that size of an engine.

  4. #4
    Senior Member MacGyver's Avatar
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    Re: SBC 350 overheating... need input

    Just thought I would drop in my 2 cents.

    If it were me having this problem. The first thing I would do is verify that your coolent is circulating properly. A point and shoot non contact therm would be good way to go. if your dash temp gauge is reading 230 degrees from your motor, and your radiator temp is much lower. You are not getting the propper flow. If it reads the same. Look at your setup. Obvious things sound silly but look at them anyway. (is the fan spinning the correct way? is their enough of a flow of air coming in as well as going out?) With the lack of a front grill on a Corvette. they use 2 Electric fans on their system. One on the front side of the radiator (sucking in) and one on the rear. (pulling out) just to keep enough air pulling through the radiator.

  5. #5
    Moderator FunnyWheels's Avatar
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    Re: SBC 350 overheating... need input

    It sounds like an air pocket in the system. You need to first park it on a steep incline and undo the highest point in the cooling system to vent out any trapped air. I then filled the engine block and system through a heater hose inlet until full. I did this on mine and it worked for a while but I also need an expansion tank to hold reserve fluid until the car engine heats up enough for the thermostat to open.

    The air in the system is the easiest to fix as well.

    Regards,

    Dave
    If you're not confused, you're not paying attention.

  6. #6

    Re: SBC 350 overheating... need input

    The Fiero has a rubber like air damn that pushes air into the radiator. Does you car still have this air damn?

    Although my money is on an air bubble in the cooling system.

  7. #7

    Re: SBC 350 overheating... need input

    Felix and I burped the system last night and got a lot of air out. I disconnected the upper rad hose and there was a lot of air in the top of the rad. I'm thinking that I may need to add two small sections of pipe tapped for a plug that I can bleed air from in the front (I have no rad cap up there). Both the upper and lower rad hoses make a small hump upwards before plunging down to run under the car. I'd be willing to bet that I've still got air in there.

    From what we did manage to get out, the car managed WAY better, but still got hot after about fifteen minutes of cruising... just a slow and steady climb to 230 or so before we shut it down.

    Next plan:

    1.) Install 160 degree 'stat again
    2.) jack up front end and disconnect both upper and lower rad hoses, filling them up from the front and reconnecting.
    3.) Run electric pump until any trapped air clears the filler at the engine.

    I'm thinking that this is strictly a trapped air issue, especially with such a marked improvement with the burping. I'm also thinking that installing the thermostat may slow the fluid down through the rad so that it can cool more before moving onto the engine.

    More updates soon!
    Meddle not with the affairs of the Dragon, for you are crunchy... and taste good with ketchup.<br />http://www.rc-sub.com/resources/grap...ni/avatar2.jpg

  8. #8
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    Re: SBC 350 overheating... need input

    Forgive my ignorance, but with my MR2 experiences I'll mention this.... Have the heat on full blast, and the MR2 has a port in the front that has a knob to mount a hose, the hose would then be taped or tied to the hood (while the hood is open) then let the car warm up and idle, the trapped air would bubble out of the tube while someone adds water to the system (in the back of MR2s), then when the bubbles stop coming the tube would fill with water meaning all the air is out of the line. it takes 15 to 20 minutes to do this too. Its always worked for me. One time I just filled water in the back and 10 min later I was on the side of the road because it started running to hot. So this is the only thing I can think of. But no matter were you put a port to bleed the system, it shouldnt matter, just have a tube (clear hose) because once it starts building up temps and pressure it will find that weakest link and start pushing all the air out! Just have it on the highest point of your radiator piping.

    Jeff

  9. #9
    Moderator FunnyWheels's Avatar
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    Re: SBC 350 overheating... need input

    Looks like you're making progress. I believe it is a trapped air issue as well. They are sometimes hard to get rid of if your radiators are higher than the motor. Electric water pumps are just fime. They move a lot of fluid without sapping horsepower. Just think about some of the race cars that have them in F1.

    Regards,

    Dave
    If you're not confused, you're not paying attention.

  10. #10
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    Re: SBC 350 overheating... need input

    There are a few things that can contribute to engine temperature. The temperature is controlled by the fan switch on the engine (and the thermostat) so regardless what modifications you do, the fan wont kick on until the preset temperature (I would toss the thermostat). I would also get a low temperature fan switch. Also make sure your fan is kicking on. Check your oil level (low oil will cause the engine to run hotter).One other thing to consider, is your fan set up for a pusher or puller? The fan might have a harder time keeping the engine cool if you have the fan is set up to push air out while driving (wind resistance).Check your air flow.
    The road to life is full of flat squirrels, who couldn't make up their mind!

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