350 chevy first time coolant bleeding/overheating help!
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  1. #1
    Rods 'n' Sods Junkie Pittaway's Avatar
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    350 chevy first time coolant bleeding/overheating help!

    ran my 350 chevy for the first time yesterday. started and ran like a dream so far. sitting at 2500 rpm to run cam in, after 5 minutes the overflow started boiling over and spewing water. i instanly killed the engine, allowed it all to cool down and then tried to find the issue, the bottom radiator hose was cool. everywhere else seemed to be ok. but to be honest as this is my first time on something like this i dont really know the right way to fill the cooling system. i just water in the engine at the moment as planning to use some nice expensive coolant once the break in is sorted.

    we tried again. keeping a keen eye on the temp guage and after another 5 minutes same again.

    the radiator doesnt seem to be giving any air out and dropping down in volume so i can fill. i was told to NOT use a thermostat for the inital process. could this be an issue?

    below are some pictures of the setup incase there might be anything untowards. im so so close and im running out of time now. i really need this thing wrapped up.
    any help would be greatly appreciated.







    thanks again for the help

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  3. #2
    Rods 'n' Sods Junkie
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    it looks like your top hose is higher than your rad cap, so you will get air trapped in the top hose.

  4. #3
    Stroker Kustom Jim's Avatar
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    I'm no expert but wonder about a few things. But also new mills, my 350 did, run hot on initial start up, I had to swtich off like you. Presume you have some kinda air blowing thru garage etc.

    The rad cap gubbins looks only just higher than the mill.
    Therefore the rad header tank isn't really above mill.
    The alternator is very verticle and is it getting a good enough grip on belt to rotate pump.
    The bottom rad hose looks a perilously tight 90* bend.

    Kapri worked in this field and hopefully will be along.

    Good luck! It looks fab
    Jimbo
    "I'm not going to take this defeatist attitude and listen to all this crap any more from all these people who have nothing except doomsday to predict."
    Carroll Shelby

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  6. #4
    Rods 'n' Sods Junkie
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    you might need one of these,

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    Official RnS Addict timbo56's Avatar
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    Is the fan working and pulling air through the rad?

  8. #6
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    all the above + could you run a mechanical fan till its not getting hot....
    my 77 vette ran in saudi heat of 50 degree plus on std mech /clutch fan and could tickover/run any speed all day long..
    re the stat if you feel the need to remove to help put an old one in with the guts removed as it helps create a little drag to the pump and circulate water round the block more evenly....remove it altogether means uneven circulation/hot spots
    perhaps jack the rad up higher till burped of all air too..
    neil

  9. #7
    Administrator blackpopracing's Avatar
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    If timing is too far retarded it will run too hot as well.

  10. #8
    Off the Xmas card list kapri's Avatar
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    You haven't got afree standing high CFM fan to push the air through when stationary plus a new engine which will produce additional heat .

    System will always have an air lock as is due to t/state houding and top hose / top of rad position.

    Water will always expand when hot and if you are filling it to the top it WILL blow out FOREVER. If you don't fill it to the top it will always have an airlock.

    Really need pukka expansion tank with pressurised cap .

    Then fill rad to top, start and run engine water will expand into recovery tank ( leave recovery tank cap off).

    Recovery tank should be half full ,empty to that level .

    Put cap back on while hot and allow to cool.

    Run it up from cold again and you should be air lock and puke free.

    Always top up if needed at the recovery tank NOT the radiator.

  11. #9
    Carburation 'sucks' Roscobbc's Avatar
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    Everything that Kapri says - including running the engine less filler cap to help vent the system - replace when engine fully warmed and water content expanded. Not in total favour of electric fans for several reasons - 1. when not operating the fan and housing presents an airflow restriction through the radiator and effectively requiring the fan to operate more often. 2. With the fan drawing cooling air only through a 'hole' equivalent to the fans diameter again the system will not be working at its most efficient (and once again the fan will possibly be operating continuously) 3. Electric fan to be efficient really needs to be set back a few inches from radiator in a 'sealed' plenum - that will ensure that cooling air is 'only' drawn through the whole radiator surface rather than a just a small area. That'll be an issue for you with obvious limited clearance between your engine and radiator.

  12. #10
    Rods 'n' Sods Junkie Pittaway's Avatar
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    Thanks for all the help and replies. I’m going to borrow a floor standing fan for the next run in,

    but more importantly I’m going to move the radiator up a few inches so it will clearly be the highest part of the cooling system and I don’t have anywhere to put a permanent expansion tank? Do you mean like a conventional header tank? Is that what you mean by recovery tank?

    Thanks again. So close now to a finished car!

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