SC detonation problem
Almost every SC in our family had detonation, current car is -93 manual with 2.73 gears. Car is stock, engine rebuilded with balanced internals. Previous owner told that he slightly cleaned intake and exhaust ports in heads during rebuild. No dtc:s and mpg is decent 28, exhaust smoke is dark when accelerating, doesn't look lean to me. No wideband installed. Exhaust gas analyzer test for inspection is good, o2 sensors work, no unburn fuel.
Spark plugs are meant for SC, platinum if I remember correctly. Car works fine but clear pinging is heard when accelerating heavily in low and mid rpms.
We had -90 and 94 automatic sc:s that both had same problem. -94 was modified - 265 hp from crank. I tuned it with Binary Editor and QH and got the pinging to minimal.
I've been told that SC:s factory tune is good and doesn't need adjustment in stock form.