Mack ASET AC, Service Manual, Page: 273 / 536

Page 260
REPAIR INSTRUCTIONS, PART 1
VALVE ROCKER ARM SHAFT
BENCH PROCEDURES
[213 LP]
Rocker Arms
Rocker Arm Improvements Effective January
2002
Effective with the January 2002 introduction of
the spring-loaded push rods, both inlet and
exhaust rocker arms have been revised to
provide pressure oil feed to the valve adjusting
screws. A vertical groove has been added to the
inboard side of the adjusting screw bore, from the
top of the bore to the oil supply hole that is just
above the bottom of the bore. On the outboard
side of the rocker arm adjusting screw boss, a
closure plug has been installed into the drilled
hole to eliminate the leak path for pressure oil
and ensure sufficient oil to the adjusting screw.
287
Figure 287 — Rocker Arm (Effective January 2002)
Further rocker arm improvements include
adjusting screws that have a groove around the
center of the screw, an oil passage cross-drilled
through the shank of the screw and an oil
passage drilled along the vertical center line of
the screw. These oil passages provide lubrication
to the ball end of the adjusting screw and the
push rod cup. Additionally, to make it easier to
hold the screw during valve adjustment, the new
rocker arm adjusting screws have a 5 mm internal
hex rather than a screwdriver slot as was used on
previous adjusting screws.
288
Figure 288 — Rocker Arm and Adjusting Screw with Oil
Passages (Introduced January 2002)
1. Plug
2. Rocker Arm (Top View) 3. Rocker Arm (Side View)
4. Hardened Pin
1. Oil Supply Groove
2. Drilled Oil Passage
3. Oil Supply Groove 4. Outboard Oil Hole
Plugged
5. Drilled Oil Hole Plugged
5-111.bk Page 260 Monday, July 10, 2006 2:26 PM