Ignition Timing

Set at 550 RPM with distributor vacuum line and parking brake vacuum hoses disconnected and taped. Transmission in "D". When timing set, tighten distributor clamp nut to 18 ft. lbs. and recheck timing to be sure distributor did not move.

All Models

5° BTDC

Fig 1: Ignition Timing Marks

Courtesy of GENERAL MOTORS COMPANY

LOW OCTANE AREAS OPERATING CAUTION: Engine fuel requirements are reduced by approximately one octane number (motor method) for each 2 1/2° that spark timing is retarded from normal 5° setting. DO NOT RETARD BEYOND TDC. DO NOT ADVANCE BEYOND 5° BTDC.