Oil pressure has nothing to do with the valve train. The 22RE is overhead cam so it has no hydraulic lifters that would maybe be noisy upon startup until oil pressure builds, very common with older V8's and such with a lifter push rod set up. Most likely the noise is the hydraulic timing chain tensioner. It could be going bad and it will take longer than usual to quiet the chain down on start up.

04' Ford Ranger XLT 4.0l (Mr. sensible)

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