CYLINDER HEAD EXHAUST VALVE GUIDE WEAR REVISED

MODELS: 1987 S/T TRUCKS AND M VANS WITH 2.5L L4 ENGINES (VIN CODE E)

Some 1987 S/T trucks and M vans with 2.5L L4 engines may experience premature exhaust valve guide wear in the cylinder head. An engine with this condition may exhibit valve train noise, missing, and a rough idle. This condition may be caused by puddled chrome on the exhaust valve stems, which results in a rough surface finish and accelerates valve guide wear.

If an engine exhibits these symptoms, measure valve stem-to-guide clearance of all exhaust valves. If one or more exhaust valve guides in the cylinder head are worn to the point where clearance is .004" to .006", ream all these valve guides to the appropriate oversize diameter, recondition all exhaust valve seats, and replace all four exhaust valves with the correct oversize valves as listed below. Valve stem to valve guide clearance and valve guide reaming procedures are on Page 6A-16 - 6A-18 of the 1987 Light Duty Unit Repair Manual. If oversize valves are not available, replace the cylinder head and all four exhaust valves with standard size valves.

If one or more exhaust valve guides are worn enough that stem-to-guide clearance is .007" or greater, replace the cylinder head and all four exhaust valves with standard size valves.

EXHAUST VALVE PART NUMBERS

P/N 10044612 - Standard Size Stem P/N 10044613 - .003" Oversize Stem P/N 10104418 - .005" Oversize Stem

CYLINDER HEAD PART NUMBER

P/N 10054501 - S/T Truck, M Van LN8

All engines have a build sequence number on a large bar code sticker located on the exhaust manifold side of the cylinder block above the oil pan rail. Engines having numbers higher than the following, which appear on the sticker, should not exhibit premature exhaust valve guide wear:

Sticker Number Models 3200559 S/T Truck, M Van

Use applicable labor time and operation number.

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.