July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Ignition Timing

Set timing at idle speed with distributor vacuum line disconnected and opening taped closed.

Without A.I.R.	5° BTDC
With A.I.R.	5° ATDC

All engines with A.I.R. are set ATDC.

Fig 1: Ignition Timing Marks

Courtesy of GENERAL MOTORS COMPANY