Timing or Octane?

[aroostok]

Had an engine rebuild about 3,000 miles ago. Recently had the opportunity to see what Betsy could do up a mountain on a long trip (200 mi. round trip). Hard to tell with all the other noises, but it sounded like the engine was starting to ping in both 3rd and 4th (no O.D.) up the mountain. This was a pretty steep mountain, but it clearly sounded like pinging.
Timing is set at 13 degrees at 1000 rpm. I'm using Sunoco 93 octane. Plugs (pulled all of them after the trip) look really great - no evidence of too lean or too rich. I'm getting over 25 miles per gallon on trips of that length (no kidding - a preacher wouldn't lie about that).
This is also an Ignitor electronic ignition.
Do I need some timing adjustment? Or do the octane additives you can find at Auto Zone and the like do any good, and if they do, what would anyone recommend?

 

[tony barnhill]

Shouldn't ping at 93-octane nor should any additives be necessary...timing issue

 

[aroostok]

Any suggestions as to which way to go?

 

[dklawson]

Retard the timing a small bit, perhaps 2 degrees. The only way to tell if the pinging is gone will be to put the engine under a similar load and listen. If it's still there, retard the timing a little bit more and repeat your load test.