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Event Coverage Just The Facts... Overheating SBCs

Discussion in 'The Hokey Ass Message Board' started by Crazy Steve, Aug 19, 2020.

  1. Water Wetter, stock fan or a black plastic Speedway Motors fan, remote trans cooler, radiator with 3 or 4 core rows. Yes flex fans do suck and will take your finger off. Cool off, winters on the way.
    Last edited: Nov 5, 2020
  2. jaracer
    Joined: Oct 4, 2008
    Posts: 595


    The only difference between ported and manifold vacuum to the vacuum advance is that with manifold you have full vacuum advance at idle. Off idle, they work exactly the same. You only get full vacuum advance when the throttle plates are open, when there is a light load on the engine. Vacuum advance is really only there for part throttle economy. Light load = high vacuum, you advance the timing. If you add load or open the throttle plates more, you lose vacuum and lose the advance. It doesn't matter if the source is below or above the throttle plates (ported).

    I should note that ported vacuum isn't the same as venturi vacuum used on the old Ford Load-O-Matic distributors.
    Blues4U, AHotRod and warbird1 like this.
  3. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 4,743


    It sounds a lot like the problem isn't with the engine itself and more with the re-engineering of that engine into a different car without proper cooling system design. The SBC ran cool in the car it came in. Believe it or not, the engineers at GM were probably pretty bright guys that knew they had to build a car to handle idling in high temps, and the system was designed to work that way. But once someone plucked that engine and installed it into God-knows what else, all bets are off.
    AHotRod and nunattax like this.
  4. "All carbureted cars were set up with direct vacuum to the distributor before more stringent emissions requirements reared their heads.

    Ported vacuum sources are a result of emissions laws and manufacturers doing whatever they could to get big V8 engines to pass smog before the incorporation of the catalytic converter."

    Above quote from the superchevy article o_O
    Total BS.... Should have known that this mythology had to come from the chevy lovers ;)
    Ported vacuum was around LONG before smog controls...

    jaracer has it right
    AHotRod and jaracer like this.
  5. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,972

    from So Cal

    Yes, ported vacuum was used as early as the 1940's, possibly earlier. But in the late 1960's to early 1970's when it was introduced on then modern engines, those engines were talking about and dealing with here, the purpose was specifically as part of the smog control devices to deal with newly introduced smog regulations.
    Peter Nowak likes this.
  6. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,301

    David Gersic
    from DeKalb, IL

    Exactly, yes. I’m reasonably sure that the OT mid 70s muscle car idled fine without overheating. Pull the engine and drop it in a 30s car, though, and all bets are off.

    Last week, I had the opposite problem. Idling downhill in 40F weather, the engine temp would drop to just over 100F from airflow alone.

    Sent from my iPad using The H.A.M.B. mobile app

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