Hummer H1 Service Manual page 107

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2-70 Engine
INSTALLER TOOL
J–39507
TOOL TAB
Figure 2-125: Seating Piston Pin Retainer Ring
Piston Ring Installation
1. Check end gap of all rings. Insert ring in bore and push it
down until its about 1-2 inches (2.5-5 cm) below top edge
of bore. Verify that ring is level, then check end gap with
feeler gauge (Figure 2-126). Correct end gaps are:
• Oil ring is 0.009-0.020 in. (0.25-0.51 mm)
• Bottom compression ring is 0.029-0.039 in. (0.75 -1.00
mm)
• Top compression ring is 0.010-0.020 in. (0.26-0.51 mm)
2. If ring end gap is correct, proceed to step 3. But if gap is
incorrect proceed as follows:
a. If gap is only a few thousandths/mm too small, file or
grind one ring end to obtain specified gap.
b. If gap is almost non-existent, or ring ends overlap,
rings are wrong size.
c. If end gap is larger than specified by only a few
thousands/mm, this indicates bore is slightly worn.
Rings may be retained.
FEELER GAUGE
RETAINING
RING
Figure 2-126: Checking Piston Ring End Gap
3. Install rings in sequence: oil ring first, bottom
compression ring second, and top compression ring last.
Use ring expander tool J–42525 to install the rings.
4. Position ring end gaps as shown (Figure 2-127). This
avoids ring gap alignment which will cause loss of
compression, blow by, and oil consumption.
5. Cover and store the piston and rod assemblies on a
workbench prior to installation.
D
C
Figure 2-127: Recommended Positioning of Piston
A - OIL CONTROL RING EXPANDER GAP
B - BOTTOM COMPRESSION RING GAP
C - OIL CONTROL RING GAP
D - TOP COMPRESSION RING GAP
Ring Gaps
®
PISTON RING
A
B