ENGINE DETONATION TIMING IS OFF

DETONATION ON 1.6L ENGINES (VIN CODE C)

Model and Year: 1985 CHEVETTE --------------

TO: ALL CHEVROLET DEALERS

Some 1985 Chevettes with 1.6L engines may exhibit detonation. On vehicles where the procedure outlined in the shop manual did not eliminate the detonation, retarding the base engine timing up to 4 degrees is permissible. Base change timing is now 8 degrees BTDC. With the maximum recommended timing change, base engine timing will be 4 degrees BTDC. This change will alleviate the detonation.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.