[maxwedge]

Engine type noises are difficult at best to try and diagnose, someone has to listen to this onsite and offer some advice as to whether it seems to be internal/lower end or in the valve train. You could pull the valve cover in the area of the noise and confirm proper valve/rocker arm actuation. A high mileage engine that has been poorly maintained could develop a sludging condition that could cause this , no way to pinpoint the issue from here.