Ignition Timing

Set timing at idle speed with distributor vacuum line disconnected and plugged.

283"

4° BTDC

327" 275 HP

8° BTDC

With Auto. Trans. & A.I.R.

⁽¹⁾ 2° ATDC

300 HP

6° BTDC

With Auto. Trans. & A.I.R.

⁽¹⁾ 4° ATDC

350 HP

10° BTDC

396"

4° BTDC

427" 390 HP

4° BTDC

425 HP

8° BTDC

⁽¹⁾	Some models with Auto. Trans. and A.I.R. are set ATDC.

Fig 1: Ignition Timing Marks

Courtesy of GENERAL MOTORS COMPANY