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1975-76 Models

  1. Visually inspect vacuum hoses and ensure distributor vacuum unit is operating. With coolant temperature below 95°F (35°C), start engine and pinch off hose between distributor and spark delay valve. See Figure.
  2. Check that vacuum advance unit operates in conjunction with throttle valve operation. As engine warms up, vacuum unit should stop functioning. If not, replace thermostatic vacuum switching valve.
  3. With engine idling, pinch off hose between "T" fitting and spark delay valve. Increase engine speed to 2000 RPM and release hose. Vacuum advance should operate 4-12 seconds after releasing hose. Return engine to idle speed and check that vacuum advance returns quickly. If not, vacuum delay valve is defective.
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