GMC T Series 1994 Repair Manual page 343

Figure 38 - Valve Guide Reaming
• I Inspect
• Valve guides for wear.
Since the valve guide serves to support and
center the valve seat grinder, the valve guide must be
serviced before reconditioning the valve seats. The
valve guide must be cleaned properly before any
measuring or servicing takes place.
@ Clean
• Valve guides, refer to Figure 36.
I Measure
• Valve guide clearance.
• If valve to guide clearances are too large, the
• Oversize Valve Availability
Reaming Valve Guides
reamer selection and usage.
VALVE SERVICE
• Valves of carbon, oil and varnish. Carbon can be
G34357— 6A— BG-EDS
• Do not scratch the valve stem with the wire brush.
• Valve stem tip for wear. The valve stem tip may
• Valve lock and oil seal grooves for chipped or
• Valve face for burning or cracking. If pieces are
• Valve stem for straightness and valve head for
- With a hole gage, measure the valve guide
I.D. and measure the valve stem with a
micrometer and compare the clearance.
- INTAKE CLEARANCE
• 0.028 - 0.066 mm (0.0011 - 0.0026 in.)
- EXHAUST CLEARANCE
• 0.035 - 0.081 mm (0.0014 - 0.0031 in.)
valve guides may be reamed oversize and an
oversized valve installed, refer to Figure 38. Do
not knurl the valve guides.
- 0.075 mm (0.00295 in.) O.S.
- 0.150 mm (0.0059 in.) O.S.
- 0.300 mm (0.00984 in.) O.S.
Refer to " Valve Service" and Figure 38 for
NOTICE:
Avoid breaking reamer flutes or
jamming the reamer into the valve guide due to
packing of chips or carbon. Clean the valve
guides before reaming.
Clean
removed with a wire brush, varnish by soaking in
carburetor cleaning fluid.
CAUTION: Safety glasses must be
worn when using a power wire brush.
Avoid inhaling of
exposure of skin
cleaning fluid, as bodily injury may
result.
Inspect
be reconditioned by grinding. Follow the grinder
manufacturer's instruction. Make sure the new
surface is perpendicular to the valve stem.
worn lands. Replace the valve if chipped or worn.
broken off, inspect the corresponding piston.
scratches may be removed with an oil
Minor
stone.
bending or distortion. Use " V " blocks. Bent or
distorted valves must be replaced.
fumes and
to carburetor