Mack MP7 - Final Steps; Valve Stem Height Measurement Procedure

REPAIR INSTRUCTIONS, PART 2
Page 279
11. Remove the sleeve installation tool from the
injector bore.
If the injector is not being installed immediately,
install the sealing plug into the injector bore to
protect it from debris.
411
Figure 411 — Unit Injector Bore Sealing Plug
Final Steps
Install the following components after
servicing the injector copper sleeves (see
ENGINE REASSEMBLY for procedures):
앫 Unit Injector(s)
앫 Rocker Arm Shaft Assembly
앫 Cylinder Head Cover
VALVE STEM HEIGHT
MEASUREMENT PROCEDURE
[213 FB]
On engines exhibiting poor performance, smoke
(at times) and a noticeable engine miss (with the
symptoms getting worse as the engine gets
hotter), may be an indication of valve seat
recession. A decrease in clearance (valve lash)
between the valve rocker and valve yoke (bridge)
can be measured at the valves to determine if
seat recession is occurring. If valve seat
recession is suspected, the following procedure
can be used to measure valve stem height. To
perform this measurement, a valve stem height
measurement gauge (tool No. 85112461) and a
depth micrometer are required.
For detailed information on rocker arm shaft
removal and installation procedures, refer to the
applicable section of this service manual.
1. Remove components as necessary to gain
access to the cylinder head (valve) cover.
2. Remove the cylinder head cover and rocker
arm shaft assembly.
On engines equipped with an engine brake, use
suitable tie straps or mechanics wire to retain the
pistons in the rocker arms. The match between
the pistons and rocker arms must be maintained.
Failure to secure the engine brake pistons before
removing the rocker shaft assembly, allows the
pistons to drop from the bore of the rocker arms.
If a piston drops out, it might not be noticed, or it
may be difficult to push the piston fully back into
the bore of the rocker arm. Also, pistons are a
match-fit to the rocker arm, and so inadvertent
mix-up of components must be avoided.
Assembling the rocker arm shaft to the engine, or
operating an engine with the engine brake pistons
not fully retracted (or missing), results in
breakage of valve train components and
significant engine damage.