Because the rocker arm fasteners are secured and tightened, valve lash is not adjustable. If a valve train problem is suspected, check that the rocker arm pedestals bolts are tightened to specification. During initial installation the bolts are coated with thread locking compound. If they are sufficiently loosened to cause valvetrain noise, they should be removed and thoroughly cleaned. Apply thread locking compound to the rocker arm pedestal bolts. Tighten the bolts to 14 ft. lbs. (19 Nm) plus 30 degrees.
When valve lash falls out of specification (valve tap is heard) and tightening the bolts does not solve the problem, replace the rocker arm, pushrod and hydraulic lifter on the offending cylinder.
Hydraulic lash adjusters are used and no adjustment is necessary.