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Technical Sbc 350 overheats at idle

Discussion in 'The Hokey Ass Message Board' started by Hotrod_hodge, Jul 20, 2019.

  1. Hotrod_hodge
    Joined: Oct 25, 2017
    Posts: 2


    Built a sbc 350. mild cam,High flow water pump,180° thermostat, dual electric fans w/ aluminum shroud they turn on at 160°. Just put the engine at 0° tdc and had to retard the distributor to bring up the rpms a bit. Driving highway sits at 180° all day. The second it hits stop and go or slow traffic it slowly climbs. I had it up to 250° the other day before getting to work. Any suggestions to fix this? I git this in a 68 impala if that helps
  2. catdad49
    Joined: Sep 25, 2005
    Posts: 3,800


    Pictures would Help!
  3. Hotrod_hodge
    Joined: Oct 25, 2017
    Posts: 2


    Sorry. 20190720_181610.jpg 20190720_181604.jpg 20190720_181610.jpg 20190720_181604.jpg

    Attached Files:

    Deuces and catdad49 like this.
  4. Professor Fate.
    Joined: Oct 26, 2012
    Posts: 64

    Professor Fate.

    That set up should not overheat. Check coolant level, check that the fans turn on AND spin the right direction, verify that the thermostat opens at 180, make sure you have "burped" the coolant system and gotten the air out of the block, check timing (with a light), it should be advanced further than 0, more like 10* before TDC with the vacuum advance plug. Should have 30-34 total timing or so which can be checked with a dial back timing light and a timing tape on the dampner. That should keep you busy for a while.
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  5. I strongly suspect the timing.......
    Deuces and INVISIBLEKID like this.
  6. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,701

    Mike VV
    from SoCal

    I don't understand this comment.
    Your engine shouldn't run at 0° of timing (at the crank).
    You should have 34° to 36° of total timing. Probably 10° to 12° at the damper.
    Low ignition timing will cause over heating.

    Truck64 likes this.
  7. ffr1222k
    Joined: Nov 5, 2009
    Posts: 1,070


    Check the fan rotation.

    If enough air passes through going down the road to cool it those fans should too.
  8. King ford
    Joined: Mar 18, 2013
    Posts: 1,280

    King ford
    from 08302

    What is your pulley ratio? If the pulleys are set up for high rpm use the water pump may not be turning fast enough at idle...remove your radiator cap and look inside to see if the water is moving at idle then speed it up. If it moves when you speed it up but not at idle that may well be the problem....I also don't understand your timing comment!
  9. brake1000
    Joined: Jan 10, 2009
    Posts: 38

    from ID

    Sounds like your timing mark on the dampner isn't correct, I would advance the timing until the motor starts to ping and then retard until it stops.
  10. Make sure your water pump is NOT for a serpentine belt set up. They spin the wrong direction for a V belt set up. I found that out the hard way. Same basic symptoms, cool at speed hot at idle.
    Last edited: Jul 20, 2019
    tb33anda3rd likes this.
  11. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,281

    from So Cal

    This is the old school way of doing it.
    olscrounger likes this.
  12. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,281

    from So Cal

    Why did you go with electric fans to begin with? I'd redo it, toss those fans in the circular file and install a mechanical fan. You may need to add some spacers to get it close enough to the radiator.

    Overheating at idle and running cool on the hay usually points to lack of air flow at idle.

    And I agree with the others advising you to get the timing sorted out, 0* BTDC is not correct. @brake1000 gave you one way to set it, that's old school, but has been done many times and works. You can also set it using a vacuum gauge, adjust the timing for highest vacuum, and then back it off slightly. Or you could verify the timing marks are accurate and set it using the timing marks. Hell, plenty of old timers did it by ear, which I've done successfully as well.
    catdad49 likes this.
  13. My old '60 Elco would Idle all day in Pomona summer heat (close to 100 deg) leaving the swapmeet. It has the stock fan, a junkyard 4 core radiator (stock for an a/c car), stock water pump, 160 deg t stat, a lumpy cam and about 10 deg initial timing.......all in a 283.
    I'm not a big fan (pun intended) of electric fans or aluminum radiators.
    Deuces likes this.
  14. 03GMCSonoma
    Joined: Jan 15, 2011
    Posts: 190


    With the engine off, we used to advance the timing so far that the engine could barely turn over. Retard the timing until it starts. Then retard it another 1/4" and tighten it up. It certainly worked on flatheads and Y-blocks.
  15. My first impression from those pictures is that there is a issue with recirculation. The path available for the fan discharge air to go back toward the front of the car and back into the radiator is very short. Also I don't see any seal between the top of the radiator or its support in the hood. Meaning there's a recirculation path from the top of the radiator also. Wasn't there a rock deflector pan under the radiator back to the front crossmember? You could experimentally cut up some cardboard and Gorilla tape it under that front end to try it out. You might go by Home Depot get a six-foot piece the largest size black pipe insulation and just for grins tape it across the top of the radiator so you've got a seal between that and the hood. That's my two cents.
    SquintBoy likes this.
    Joined: Jul 20, 2006
    Posts: 2,071


    This is the correct way advance to maximum vacuum, then back off the timing slightly.
  17. vickckik
    Joined: Dec 21, 2011
    Posts: 70


    My experience was similar to Scotty T's. I had a leaking pump replaced. The mechanic thought all 350s used the same pump so he got one off the shelf and installed it. It took me a week to determine the problem. When I returned to the mechanic he suggested hoses, thermostat, radiator, heater core and timing. After some persuasion he pulled the new pump. and found he had put a serpentine pump on a v-belt engine. With many sincere apologies he installed the right pump and also a new thermostat and all hoses on his dime.
    SquintBoy likes this.

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