mid year big block running hot

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  • Joe L.
    Beyond Control Poster
    • February 1, 1988
    • 43133

    #31
    Re: mid year big block running hot

    Originally posted by Duke Williams (22045)
    But as you go into the seventies you find that centrifugal curves were shortened and initial timing was less than antecedant pre-emission engines. Vacuum advance was often more, but only at very high manifold vacuums.

    The '74 Califronia L-48 automatic, which probably represents the worst of the lot, is speced at 4 deg. initial and has nominally 18 degrees full centrifugal at 4200, so at WOT high revs total advance was only 22 degrees vs. the optimum of 38. That took a huge hit on peak power!

    I don't think it had to been this way as WOT, high revs was never a part of the emission certfication procedure, but as Dave McClellan said in his book, sometimes they were up against the wall to get an engine/drivetrain configuration certfied in time to have a product that could be sold on announcement day, so the goal was to get the car certified whatever the cost in power.

    Duke
    Duke-----


    The 70-74 models with CCS were unquestionably the worst. That's why I prefer AIR to CCS. However, some of the 72-74 may have had elements of CCS combined with AIR.
    In Appreciation of John Hinckley

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    • Glen C.
      Very Frequent User
      • November 1, 1985
      • 193

      #32
      Re: mid year big block running hot

      Here's what fixed my L72 over heating problem. A properly calibrated gage sending unit. It took three to find a good one. New Dewitt aluminun "Direct Fit" radiator & new reproduction fan shroud. Changed the ported vacuum to full time, (Thank you Duke) & changed the vacuum can to a VC1765 aka B26. Here's a bonus, hook up a "puke" bottle next to the radiator. Gage never goes over 180* and I'm in Florida.

      Comment

      • Michael J.
        Extremely Frequent Poster
        • January 27, 2009
        • 7033

        #33
        Re: mid year big block running hot

        The puke bottle is especially handy to save your garage floor after a long cruise in hot weather......
        Big Tanks In the High Mountains of New Mexico

        Comment

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