I bought my Dakota a year and a half ago. And it had a bit of a tap when I bought it. At first it was more akin to an exhaust manifold crack. I've always used 10W-30 since I've had it, and have never had any problems. On my most recent oil change, I did an engine flush, and put 10W-30 synthetic oil back in.
Since, the tap has gotten much louder, and is becoming worrisome. At start up, the engine is quiet. After maybe fifteen seconds, the tapping starts, and is sort of loud. The oil pressure sits between 40 and 110 psi.
After a few minutes, the tapping quiets significantly, and the oil pressure subsides to just under 40 psi.
I should mention, that on cold starts, it starts fine (except for the check valve in the tank being bad causing me to have to turn the key a couple times to "prime" it) runs choppy for a few seconds, then runs fine after.
I'm thinking my problem may be one or more of a few. One being stuck lifters. Another being maybe bent push rods (although it doesn't run rough). My third option is poor oil delivery.
Any insight or suggestions would be greatly appreciated.

 

Sometimes synthetic oil makes your lifters sound louder happened to me but for me it was switching from one synthetic to another synthetic.

In the long run your lifters are just a little worn the synthetic oil just exposes it.

Other problem is low zinc even synthetic oil has less zinc these days Google it I used zddp maxx additive in my oil it quieted my lifters by half.

https://www.amazon.com/Zddp-Maxx-Oil.../dp/B003MS6QHS

http://www.zddpmaxx.com

 

Start by pulling the valve cover. Make sure the rockers are fully seated.

Could it be a leaking exhaust manifold? They can sound like a tap and quiet down as it warms up.

 

I thought exhaust manifold at first, but after it warms up, the tapping gets much quieter, but sadly sounds a bit like either main bearings, connecting rod bearings, or maybe timing chain noise. Thinking about either buying a reman, or doing a rebuild.

 

If it's toast and you are going to be rebuilding/removing it, You may as well drop a 5.9 in there.

 

Thought about dropping a 5.9 in. I would love to have some V8 power, but then that means buying another transmission, wiring harness, and ECM.