In my 92 350 cab and chassi there is hardly any blowby either which is comforting but a while back the engine started to knock hard when first accelerating. I let off of the pedal and step on it again and it goes away. Quiet at full speed. Maybe a sticking valve I don't know. Great oil pressure, 55lbs at start up and when warm stays at 40lbs.
There is a high pitched squeal when I take off the oil filler cap with engine running, was checking for blowby the other day and can hear it. Been that way pert near 3 years now. Truck starts immediately every time though, within 1/2 second (as long as glow plugs are hot or engine is real warm).