68496 Mercruiser SCREW (3/8-24 X 2-1/4 IN.)

Illustration 1 g00489792
(1) Rocker arm shaft Bore in the rocker arm for shaft ... 24.803 0.013 mm (.9765 .0005 inch) Diameter of the rocker arm shaft ... 24.752 0.013 mm (.9745 .0005 inch)
Illustration 2 g00489795
(2) Apply 5P-3931 Anti-Seize Compound to all of the threads of the bolts that hold rocker arm shafts. Tighten the bolts in the step sequence that follows:
Tighten bolt (1) through bolt (6) in sequence.Tighten the bolts to the following torque. ... 270 25 N m (200 18 lb ft)
Tighten bolt (1) through bolt (6) in sequence.Tighten the bolts to the following torque. ... 450 20 N m (330 15 lb ft)
Tighten bolt (1) through bolt (6) in sequence.Tighten the bolts to the following torque. ... 450 20 N m (330 15 lb ft) (3) Valve adjusting screw locknut Tighten the valve adjusting screw locknut to the following torque. ... 47 9 N m (35 7 lb ft) (4) Bridge adjustment screw Tighten the bridge adjustment screw locknut to the following torque. ... 30 4 N m (22 3 lb ft) (5) Valve lash Intake valves ... 0.38 0.1 mm (0.015 0.004 inch) Exhaust valves ... 0.76 0.1 mm (0.030 0.004 inch) (6) Height to top of dowel ... 53.3 0.5 mm (2.10 .02 inch) (7) Dowel Diameter of the dowel ... 11.008 0.003 mm (.4334 .0001 inch) Bore in bridge for the dowel ... 11.13 0.05 mm (.438 .002 inch) Bore in head for dowel ... 10.968 0.020 mm (.4318 .0008 inch) (8) Valve lifter Diameter of the valve lifter ... 27.896 0.013 mm (1.0983 .0005 inch) Bore in the block for the valve lifter ... 27.953 0.019 mm (1.1005 .0008 inch)Note: Refer to Guideline For Reusable Parts, SEBF8069, "Salvage Of Lifter Bores in 3400 Family Engines" for the salvage procedure of the lifter bores in the cylinder block. (9) 6N-6872 Guide Spring Note: Refer to Guidelines For Reusable Parts, SEBF8066 for information on reusing guide springs.
Illustration 3 g00489797
(10) 2N-7229 Spring Length under test force ... 74.2 mm (2.92 inch) Test force ... 45 to 53 N (10 to 12 lb) Free length after test ... 114.3 mm (4.50 inch) Outside diameter ... 29.7 mm (1.17 inch) (11) Dowel length above top surface of rocker shaft support ... 12.7 1.0 mm (.50 .04 inch) (12) Clearance for rocker arms (both ends) ... 0.30 to 1.40 mm (.012 to .055 inch) (13) As needed, use the 2N-7228 Washer to achieve clearance (12).
Illustration 4 g00505960
Valve Bridge (A) Minimum dimension after reconditioning ... 16.51 mm (.650 inch) (B) Allowable wear before reconditioning ... 0.13 mm (.005 inch)An inspection for wear should be performed on the seat of the bridges. Use the bridge again if the wear is less than 16.51 mm (.650 inch). If the wear seat is worn more than the allowable limit, the worn surface of the seat can be ground flat. The maximum amount of material which can be removed is 0.13 mm (.005 inch). If the seat cannot be machined flat, replace the bridge. You may recondition the seat once.