CUMMINS S3.8 - Section 7 Checking Valve Timing

Section 7
CHECKING VALVE TIMING
1. Attach suitable graduated disc to the vibration 180
0
in order to bring No. 1 piston to BDC
damper pulley and mark ‘BDC’ position on
the periphery of the vibration damper pulley
by turning crankshaft by 180 from ‘TDC’
position. Fig. 7-1.
2. Remove cylinder head cover.
3. Adjust valve clearance (inlet 0.2 mm; outlet
0.3 mm). Eliminate No.1 inlet valve clearance
by inserting a 0.2 thick feeler gauge between
valve tip and rocker. Fig. 7-2.
4. Turn crankshaft to bring No. 1 piston to TDC.
(compression stroke). In this position, valves
of the No. 6 cylinder will be overlapping.
Fig. 7-1
5. Attach magnetic stand with dial gauge to the
cylinder head in such a way that the
plunger of the dial gauge rests on the
spring retainer of the 1st cylinder inlet valve
with a preload of about 10 mm. Position
plunger on the spring retainer as away as
possible from the centre to avoid fouling of
the rocker. Adjust dial gauge pointer
(bigger) to zero and also note down the
reading of the smaller needle.
6. Turn crankshaft clockwise slowly through.
3600 to bring No. 1 piston just to TDC II
position (end of the exhaust stroke). Do not
turn crankshaft in anti- clockwise direction to
adjust TDC position.
7.The difference between dial gauge readings
will give valve lift. The valve timing is correct
if the lift indicated by the dial gauge is within
the specified value of 0.8+ 0.2 mm.
8. The valve timing can be counter checked by
turning the crankshaft clockwise further by
Fig. 7-2
II position (End of the suction stroke). Note
down the dial gauge reading when the BDC
position is just reached. The difference
between this and the initial dial gauge reading
will give the valve lift in this position. The
timing is correct if the lift is within the
specified value of 3.9+ 0.3 mm.
9. Valve timing can also be ascertained by
checking the lift of the exhaust valve. To be
doubly sure, it is preferable to check the lift
of the exhaust valve of No. 6 cylinder. The
valve lift at BDC I (end of power stroke) and
TDC II (end of exhaust stroke) should
correspond to specifications.
10. Valve lift readings beyond the specification
suggest wrong valve timing possibly on
account of worn out crankshaft - camshaft
Workshop Manual
S3.8 Engine
A030K288 (Issue 2)
01-2010
29
*
NOTE : Before reaching the TDC
position, preloaded plunger of the dial
gauge will move along the spring
retainer of the valve. Note down dial
gauge reading when the TDC position
is just reached.