Engine - Valve Train Noise/Miss/Rough Idle
87chevy11GMC NUMBER: 87-T-64
GROUP: 6E - Engine Exhaust
DATE: July, 1987
CORPORATE
NUMBER: 736013
SUBJECT: CYLINDER HEAD EXHAUST VALVE GUIDE WEAR
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.