Most Pontiac engines like total timing (rev engine past 3000 or so until the mechanical advance stops moving/advancing, vacuum advance disconnected to check total timing) somewhere between 32 and 36 degrees. Setting initial timing at idle with the vacuum advance disconnected will usually fall around 12 to 16 degrees, but that's not really important. What is important is the total timing, the initial timing + the mechanical/centrifugal advance that's built into the distributor (springs and weights). So look for about 36 total, then back off a little (2 degrees at a time) if the engine rattles (pre-ignition) in high gear when you nail the throttle at a moderate speed, say 30-35 MPH. Sometimes a little more for lower compression engine at higher altitudes, I run 38 degrees total in my '74 455 with 8.6:1 compression. Runs 12-flat 1/4 mile times at 110 MPH on 91 octane, Pontiac torque does the job. Congrats on owning the only known '69 455, us Pontiac guys all think that '70 was the very first year for the 455. Just funnin' with ya, good luck.
One thing to be aware of, for several editions of the Motor manuals they had the arrow pointing the wrong way on the distributor rotation picture for Pontiacs. Can't begin to tell you the headaches that caused mechanics back in the 70's.
Good point. When I was arranging the plug wires on my first Poncho engine, I mistakenly put them in a clockwise firing order. WRONG! Our Pontiacs have a counter-clockwise distributor rotation.
I checked the firing order so many times the weekend that I first started my 421SD that I still have it memorized 40 years later. It was always up on #1 compression stroke when I checked it.
The Jalopy Journal
