Checking the clearance in the camshaft bearing journals
Camshaft journal diameter
Measure the camshaft journal diameter with a micrometer (A).

Inner diameter of the main bearing bore in the cylinder head
Using a bore gauge, measure the inner diameter (A) of the hole in the cylinder head.

Clearance in the camshaft bearing journal
Calculate the gap size using the formula:
(Oil clearance) = (Inner diameter of the hole) - (Camshaft journal diameter)
If the obtained value exceeds the norm, replace the camshaft and/or the cylinder head assembly.
Note: The upper cylinder head is not replaced separately from the cylinder head, as both parts are machined together at the factory. Replace the upper cylinder head only as a complete unit with the cylinder head.
Material borrowed from the website: www.NissanBook.ru