The common suggestion that most hot-rodders make when faced with this problem is that the valve guide seals ... combine with intake manifold vacuum to push oil from the lifter valley directly ...

If a valve lash is set incorrectly, this can cause lifter tick. Improper lubrication can also cause valve noise. This can be due to low oil pressure ... from a cracked manifold, faulty manifold ...

Its overhead-valve, two-valves-per-cylinder arrangement ... Under cylinder deactivation, the Lifter Oil Manifold Assembly (LOMA) routes oil to the necessary lifters via four lifter-oil solenoids.