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66 tune up

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  • John F.
    Very Frequent User
    • July 31, 1999
    • 105

    66 tune up

    I'd like to do a tune up on my 66, 327/300. The manual indicates that timing should be set at 6 deg. advance. Given that I'm burning 93 oct. unleaded gas, does that change the timing requirements? The car has been sitting for some time, and seemed to run fine before I began the other work, although it got very poor mileage, 9-10 mpg. Also should timing be checked at other than idle rpm? Thanks

    John
  • Duke W.
    Beyond Control Poster
    • January 1, 1993
    • 15610

    #2
    Re: 66 tune up

    Start with the recommended 6 degrees. If you observe detonation back it off a couple of degrees.

    I recommend a thorough inspection of the distributor. Check the centrifugal and vacuum advance systems against spec which are listed in the '66 chassis service manual and the AMA specs. A dial back timing light and vacuum pump and gage are very useful to do these checks.

    Your car should be achieving better fuel mileage than you report, so their could be a problem with the ignition map.

    duke

    Comment

    • Jack H.
      Extremely Frequent Poster
      • April 1, 1990
      • 9906

      #3
      Re: 66 tune up

      Your engine, if built stock, wasn't aggressively high on compression ratio and should run well with standard high octane pump gas. Poor fuel milage depends a LOT on how one drives with economy falling for those who are aggressive on the 'fun factor' of acceleration in stop/go traffic.

      If the advance mechanism(s) of the distributor are faulty (hardened grease keeping the centrifical weights from moving freely, vac advance can leaking), you CAN expect fuel milage to drop appreciably. Checking the mechanical advance is pretty simple...

      Remove the dist cap and move the centrifical weights by hand. If they're sticky to any extent, clean the mating surfaces and re-lube.

      On checking the vacuum advance can, there are several threads in the archieves for how to verify TOTAL advance performance using a dial-back timing light.... Lack of proper vac advance WILL reduce fuel economy will you're crusing at highway speeds!

      Comment

      • John F.
        Very Frequent User
        • July 31, 1999
        • 105

        #4
        Re: 66 tune up

        Thanks for the good advice guys.

        john

        Comment

        • Jim T.
          Expired
          • March 1, 1993
          • 5351

          #5
          Re: 66 tune up

          John the advice Jack gives you about your 66's distributor is very good. Back in 68, my 64 Corvette just was not running right after warming up. Cleaned up and lubricated the centrifical advance sure made a difference. It was remaining advanced after it got hot. While you are checking this, pull the tach gear drive from the distributor and give it a cleaning and lubrication so won't fail and require replacement of the gear and distributor shaft, so much cheaper to lubricate.

          Comment

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