INABILITY TO SET IGNITION TIMING

VEHICLES AFFECTED: 1987 JB WITH OPT LT2 OR LT3 2.0L OHC ENG (VIN CODE K OR M --- JB = 'J' SERIES

Early build LT2 and LT3 enqines used a crankshaft dampner that could experience an outer "Timing" ring rotation relative to the inner crankshaft drive. The result is the inability to check or set spark timing after clistomer usage.

A new crackshaft dampner pulley, P/N 10083143, repairs the original outer ring slippage. .Below are the break points of potentially affected vehicles.

Car Line Engine VIN VIN Break Point

Pontiac K SOP to H7566886

Pontiac M SOP to H7567626

Buick K SOP to HK427650

Buick M SOP to HK443011

Oldsmobile K SOP to HK316380

Use applicable Labour Operation and Time.

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.