2. When the head is returned from the workshop, the valves and associated components will already be installed. In this case, skip the procedures in the next two paragraphs and proceed directly to the actions described in paragraph 5.
3. Lubricate the valve stems with liquid oil and insert them into their guide bushings. Install the valve spring seats.
Note: On SOHC engines, each valve spring has a (internal and external) a separate seat is provided. The outer spring seat must be installed first, then the inner one. Place new oil-deflecting caps on the guide bushings through the valve stems.
On DOHC engines, the valve stem seals are seated on their guide bushings by gently tapping them with a hammer through a special mandrel or socket of the appropriate size. On SOHC engines, a special device should be used to seat the intake valve stem seals; exhaust valve stem seals can be seated by hand. Make sure that the stem seals are not twisted on the bushings.
4. Install the valve spring(s) and its retainer on the stem. Using a special tool, compress the springs by lowering the retainer, then install the split lock crackers into the open upper groove on the valve stem. In order to temporarily fix the crackers until the tool is released, lubricate them on the inside with thick grease. Slowly release the spring(s) and make sure that the crackers are securely seated.
Note: On SOHC engines, each valve is equipped with two springs. First, insert the inner spring into the outer one, then the entire assembly is seated on the valve. On all engines, the springs are installed with the end with the reduced pitch of the coils facing the head.
5. On DOHC engines, reinstall the valve lifters and camshafts.
6. On SOHC engines, install the camshafts, tappet guide assemblies, and rocker arms with axles.
The original is available on the web page NissanBook
7. Make sure that the old components removed from the head that are to be used further are installed strictly in their original places.