Note: tapping clanging when first started up that diminishes as it warms up

O=The AJ133 is an incredibly well engineered engine. some of the major changes affecting it are the oil anti drain back valve is no longer in the spin on oil filter, there is no spin on oil filter and the top access filter is jut that only a filter, when the engine is shut down it empties back to the crankcase. There is an oil cooler in the valley between nthe banks, affixed to it is the anti back flow valve.
The system for advancing and retarding the 4 ncamshafts works off the pressure of cam ramp up and back down, the cam gear variators are fitted with a complex set of pistons that route oil pressure to fill or exhaust the void of adv and ret they are controlled by four solenoids via the ecm . The cam chains are very well oiled by dedicated sprayers, thoughthe loss of pressure when shut down will alow thecam ramp pressure to rotate the gears and pull slack the non pressure side of the chain. In the instance of this and also the drainback valve leaking when you start it it will make the gears clack back and forth on the rampu and ramp down until the oil pressure is restored, it sounds like the engine is going to explode. Non supercharged models have hydraulic tappets for the intake side, This supercharged model is my second x 351 the first was naturally aspirated. there is much more to this story the X 40 was hit while stopped and totaled what a shame. I am becoming expert on the x351 incrementally