Spring Loaded Scraper Ring; To Fit Piston And Connecting Rod Assemblies; Fitting New Pistons - Perkins 4.108 Workshop Manual

The gaps of the remaining rings should be stag-
gered alternately along the gudgeon pin axis.
Liberally lubricate the rings in their grooves and
see that they can move freely in their locations,
this does not apply to the laminated type in the
fourth groove, which if correctly fitted should not
move freely due to the outward pressure of the top
and bottom segments on the ring groove walls.
When all the rings have been fitted, they should
be shown in Fig. F.9.
Always ensure that internally stepped or taper faced
rings are correctly fitted. They are marked TOP or
BTM (bottom) to ensure correct replacement.
The top compression and slotted oil control rings may
be fitted either way up.
Spring loaded Scraper Ring
When fitting the chrome plated spring loaded scraper
ring. (see Fig. F.1 0). the following procedure should
be adopted:-
1. Fit internal expander (1).
2. Fit two rail rings (2) at the bottom of the groove.
3. Fit spiral ring (3).
4. Fit two top rail rings (2).
When fitting rail rings, the gaps should be staggered.
To Fit Piston and Connecting Rod Assemblies
Before fitting the piston and connecting rod assemblies
to their respective cylinder bores, thoroughly clean
and liberally coat each bore with clean engine oil.
1. Turn the engine until the crankpins of numbers
1 and 4 cylinders are at the bottom dead centre.
2. Using a suitable ring clamp of the type shown in
Fig. F.11, carefully compress the rings of No. 1
piston and hold in this position.
3. With the word 'FRONT' on the connecting rod
facing the front ot the engine, insert the rod care-
fully into No.1 cylinder bore.
NOTE: The cylinders are numbered 1, 2, 3, 4
starting from the front (water pump) end of the
engine. It is extremely important that these com-
ponents (marked as shown in Figs. F.4 and F.5),
are returned to their original locations.
4. The piston head may be gently tapped with the
shaft of a hammer as shown in Fig. F.11 until all
the rings have entered the cylinder bore.
5. Draw the rod towards the crankpin, place the top
half bearing shell in position locating the tag in
the machined slot and liberally oil, draw the rod
onto the crankpin.
6. Fit the lower half bearing shell to the connecting
rod cap, locating the tag in the machined slot,
liberally oil and fit the cap to the crankpin, ensur-
ing that the numbers on the rod and cap coincide
as shown in Fig. F.4.
PISTONS AND CONNECTING RODS-F.S
F11
7. Fit the two connecting rod securing setscrews and
tighten evenly to the torque quoted on Page B.2.
NOTE: Locking tabs are not fitted to these set-
screws.
8. Repeat this procedure for No. 4 piston and con-
necting rod assembly.
9. Rotate the crankshaft to bring numbers 2 and 3
crankpins to bottom dead centre.
10. Repeat procedures 2 - 7 to fit the two remaining
assemblies.
11. Refit the lubricating oil sump. (Refer Page L.4).
12. Refit the cylinder head assembly. (Refer Page
E.7).
Fitting New Pistons
With new 4.108 and 4.107 pistons a machining allow-
ance is provided on the crown of the piston to enable
the necessary material to be removed by means of a
lathe so that when fitted the piston height above the
cylinder block top face will be within the limits quoted
on Page B.3.
To determine the exact amount to be removed from
the piston crown, the piston, connecting rod and bear-
ing assembly will have to be fitted to its respective
cylinder bore as previously described, and the piston
height above the cylinder block top face measured
with the particular piston at top dead centre. This
piston height can be measured by means of a piston
height gauge of the type shown in Fig. F.12. Repeat
for each new piston to be fitted and mark each piston
with the number of the cylinder bore it will belong to,
(not on the top as any marking here will be removed
by the machining). When each piston has been
skimmed it should be checked again when finally re-
fitted to ensure that any new piston fitted is now within
the limits quoted. Once the piston height is correct
mark any such piston on the crown with the number
of its respective bore. (Refer to Fig. F.5).
Pretopped pistons are available for fitting to 4.108
vehicle engines and all 4.99 engines and are available
in three grades (see separate tables). For identification
purposes, the grade letter is stamped on the piston
crown.