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Vacuum Advance Schedule Test

  1. While proceeding through following test, be sure to check each specification when indicated. See appropriate table in DISTRIBUTOR SPECIFICATIONS section of this manual.
    CAUTION: Use of a rubber exhaust tube for ventilation may result in fire due to high temperatures experienced during this test. Only use a metal exhaust tube.
  2. Connect magnetic timing probe or adjustable timing light and tachometer to engine. Start engine and warm to normal operating temperature. If already at operating temperature, wait at least 1 minute for Start Up Advance to return to basic timing. Put transmission in Neutral and apply parking brake. Perform the following steps and check in order:
    • If necessary, check and adjust basic timing. Remove and plug vacuum hose at vacuum transducer.
    • Disconnect carburetor switch from ground connection. Increase engine speed to 1100 RPM.
    • Check "Speed Advance Timing", timing should be as specified in Distributor Specifications.
    • With engine at 1100 RPM, connect vacuum hose to vacuum transducer. Allow accumulator in computer to clock up. Refer to Distributor Specifications for correct clock up time.
    • With accumulator clocked up and engine still at 1100 RPM, check "Vacuum Advance", it should be as specified in Distributor Specifications.
    • Disconnect and plug vacuum hose at transducer and run engine at 1500 RPM (3000 RPM for 4 cyl. engines).
    • Note "Speed Advance Timing". Connect vacuum hose to vacuum transducer.
    • Check "Vacuum Advance", it should be as specified in Distributor Specifications. Return engine to curb idle, connect carburetor switch to ground.
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