Yes you can, as long as you did not bother the other ones. Just adjust the one you replaced.
replace the hydraulic tappets in the rocker arms, valves are non adjustable.
Collapsed hydraulic valve lifter? Rocker arm (valves) need adjusting?
Everyone I know says 25 foot pounds but you really need to go online because you are adjusting the valves and there is a specific order for doing it.
Adjusting the valves on a Caterpillar C 15 Engine is easy and does not take long at all. All you need is a wrench and a feeler gauge, You will then loosen up the bolt, place the feeler gauge in between the rocker arm and valve and then turn the wrench until the rocker arm touches the feeler gauge.
Either that or remove the rocker arms and do a cylinder leakage test.
Bring the piston up on tdc right after the intake valve closes and then loosten the adjusting nut until there is slack in the rocker arm. Tighten it down until the slack is gone,{you can tell by turning the push rod} then turn it 3/4 more. Do this on all cyls.
take off the valve covers, and the rocker arms will have adjusting nuts on them, tighten them to zero lash and the back off 1/4 turn.
You can adjust tapping valves by adjusting the lifters.
The best way to tell if the valves are closed is to observe the rocker arms. When they are both at the top of their travel, valves are closed. Feel the rocker arms and try to move them, if they move their at the top of their travel.
They are not adjustable.
To adjust the valves on an Oldsmobile 403 engine, first ensure the engine is cold and remove the valve covers. Use a feeler gauge to check the clearance between the rocker arm and the valve stem, adjusting as necessary by loosening the lock nut and turning the adjusting screw to achieve the specified clearance. Repeat this process for each valve, following the correct firing order, and recheck clearances after adjustment. Finally, replace the valve covers and ensure all fasteners are tightened to the manufacturer's specifications.
you are probably refering to a rocker arm. In a pushrod motor the rocker are opens the valves. A rod rides on the camshaft and as the lobes on it come around the rod pushes up on the rocker are which does exactly that, rocks the same as the rocker on a rocking chair . The rod pushes up on the rocker which then pushes down on the valve, opening it.