Engine tapping noise

Your mileage may reflect a good bit of wear, on every part of the valve train!

Maybe your Tappets (lifters) are not operating as they should, because of goop/carbon buildup/anything similar you might try this:

Do an oil change, substitute 1 qt. Of Marvel Mystery Oil for 1 qt of motor oil. This will clean and free up the internals of your tappets.

Tappets readjust to zero for the push rods (all involved parts)slack/ slop/ wear (every time they drop down into oil pressure in the oil galley, that they ride in). They open and refill and take-up any slack. Upon raising up they Close off and function much like a hydraulic jack, oil has refilled the slack void that was there when they traveled downward.

. Unless "crap" prevents the tappets from sealing off to act kind of like a hydraulic jack. This is referred to as a leaking tappet/lifter The Marvel Mystery Oil may clean them up and fix the leaking issue!

You can run it until the next oil change oil change w/Marvel Mystery Oil. (It can be run every oil change if you want). I usually do it once to clean my tappets on one oil change. I use an oil stabilizer (such as Hi-Tach or Lucas) substitute it for a qt. Of oil during all future oil changes.

Pic below, see the many parts crammed in such a small container?
You may be able to clean them up with the Marvel Mystery Oil. Missing those oil changes does not help!

Keep us posted.

The Medic