Hello all, it's been a long time since I posted here.

Here's my problem:

While car is warming up, engine sounds fine. As is it starts to get up to temp, I hear a tapping sound. While driving down the highway, the sound is tapping/rattling especially underload (it is not spark knock type rattle). I believe one of my lifters has finally let go (origional lifters-160k+ miles on them). Just thought I would get an opinion or 2 before I pull the manifold or worse the block.

Thanks,

Sparks a flyin'

 

If the lifter is bad its bad. It won't be ok when cold and noisy when its hot. Whats the oil pressure look like when its cold vs hot?

 

sounds like the classic exhaust noise vs lifter noise dilemma.
go to a local pharmacy and buy a cheap stethescope(the thing your doctor listens to your heart with) replace the part normally applied to the chest with a 1/4-20 bolt,then play doctor with your engine!touch the bolt to the valve cover over each rocker arm.if one sounds louder than the others,you've found the offending area!double check the preload(i prefer 1/4 turn warmed up and running)on the offending rocker.if it doesn't get better it's probably a bad lifter.
if all the rockers sound pretty much the same,it's likely an exhaust leak!
you will get lots of use out out of that cheap stethescope!
also handy for diagnosing worn bearings,bad water pumps,and dozens of other wierd noises on your(and other people's)cars!
( hot chicks will flock to you and you will probably win a nobel prize for achieving world peace!not to mention,your mother in law will be proud of you! )
seriously,worth the investment!
Eric B