Hummer H2. Manual — part 61

Fig. 3: Checking Cylinder Head for Warpage

VALVE SPRINGS

Inspect valve springs for corroded or pitted valve spring surfaces which may lead to breakage. Polished spring
ends caused by a rotating spring indicate that spring surge has occurred. Replace springs showing evidence of
these conditions.

Inspect valve springs for squareness using a 90-degree straightedge. See Fig. 4 . Replace valve spring if out-of-
square exceeds manufacturer's specification.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 4: Checking Valve Spring Squareness

Using vernier caliper, measure free length of all valve springs. Replace springs if not within specification.
Using valve spring tester, test valve spring pressure at installed and compressed heights. See Fig. 5 .

Usually compressed height is installed height minus valve lift. Replace valve spring if not within specification.
It is recommended to replace all valve springs when overhauling cylinder head. Valve springs may need to be
installed with color coded end or small coils at specified area according to manufacturer.

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 5: Checking Valve Spring Pressure

VALVE GUIDE

Measuring Valve Guide Clearance

Check valve stem-to-guide clearance. Ensure valve stem diameter is within specification. Install valve in valve
guide. Install dial indicator assembly on cylinder head with tip resting against valve stem just above valve
guide. See Fig. 6 .

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures

Fig. 6: Measuring Valve Stem-to-Guide Clearance

Lower valve approximately 1/16" below valve seat. Push valve stem against valve guide as far as possible.
Adjust dial indicator to zero. Push valve stem in opposite direction and note reading. Clearance must be within
specification.

If valve guide clearance exceeds specification, valves with oversize stems may be used and valve guides are
reamed to larger size or valve guide must be replaced. On some applications, a false guide is installed, then
reamed to proper specification. Valve guide reamer set is used to ream valve guide to obtain proper clearance
for new valve.

Reaming Valve Guide

Select proper reamer for size of valve stem. Reamer must be of proper length to provide clean cut through entire
length of valve guide. Install reamer in valve guide and rotate to cut valve guide. See Fig. 7 .

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Engine Overhaul Procedures