preignition problem

[89SE-ICoupe]

My car is completely stock with 131,000 miles on it. When I accelerate hard ( i.e. getting on the freeway) and put the engine under heavy load I get preignition. I have tried using 93 octane fuel but that does not work. I also checked the ignition timing (15 degrees BTDC) and it is accurate, although the mark on the flywheel does not hold steady when the timing light is aimed at it. Could it be a problem with the vacuum advance mechanisim? If anyone has any suggestions as to what is causing this, it would be greatly appreciated.

[AZmike]

Sounds like you're right and your vacuum advance isn't working properly. I bet another distributor would solve your problem.

[johnwc723]

maybe your compresssion is SUPER HIGH, and you need race car fuel *wink* i dobut it