Relative to their EJ Phase I predecessors, the pistons for the EJ251 and EJ252 engines had reduced piston pin offset and a molybdenum coating to reduce friction.
The hydraulic lash adjuster — located at the fulcrum of the roller rocker arm — consisted primarily of a plunger, plunger spring, check ball and check ball spring.
To alter cam timing, the spool valve would be activated by the cam timing oil control valve assembly via a signal from the ECM and move to either the right to advance timing or the left to retard timing.
Due to the cylinder head offset, the left camshaft was longer than the right camshaft to align the cam belt sprockets.
The camshaft timing gear assembly contained advance and retard oil passages, as well as a detent oil passage to make intermediate locking possible.
As a result, the hydraulically-controlled camshaft could not respond to ECU signals.
Pressed by hydraulic pressure from the oil pump, the detent oil passage would become blocked so that it did not operate.
Cylinder head: camshaft and valves The FA20D engine had an aluminium alloy cylinder head with chain-driven double overhead camshafts.