Because the KA24DE has no rocker arms, the adjustment of valve
clearences is performed be swapping out shims on top of the
lifters. The cams actually act directly on these shims, allowing
them to dictae the clearence. Without the special Nissan tool, the
only way to change these shims is by removing the cam shaft. The
most efficient method of doing this is to note the current
clearence of all eight valves (eight per cam), remove the cam, then
measure the existing shim. Then figure what sized shim you need.
For example, if the FSM calls for .009 and you had .012 then your
new shim should be .003 thicker than the existing. Take not that
the FSM specified clearences are HOT. Therefore you should allow an
additional .002 or so. After running the engine to temp, you should
check all clearences again.