I have what sound like a lifter tap, only on start up? it goes away after about 10 to 30 seconds and it only happens if it sets more than 4 hours.

the motor was replaced by the previous owner, and from what he says it came out of a rolledover truck. anyone have any ideas befor i rip this thing apart and put lifters in it?

 

Generally thats normal because when the motors not running oil will seem back down into the oil pan of the motor as compared to oil throughout the motor when running. Mine does it too and will go away after about 30 seconds. I put in a quart of Lucas Oil Stabilizer for more protection because your cold starts are very crucial to a motor. My motor is a very noisy motor anyways. You can hear it slightly after it warms up and normal driving anyways, ive always known them to be noisy.

P.S. You should hear my buddies Durango with dual overhead cams when he starts it up till it gets oil up there haha

 

If it is the 4.3L then I would look for sludge in the oil.
Either change the oil and look for it to gloop out at times or remove the valve covers and look for sludge build up in the valve covers.
If you have sludge in the oil, then replace the intake manifold gaskets.
If you have severely overheated the engine, do what I'm doing to my daughters 2004Jimmy ZR2. Buy a 4.3L problem solver gasket kit and replace the head and intake gaskets. Also have the heads and manifolds checked for warping and of cracking.
I have a kit like this.
http://www.amazon.com/dp/B0016OMSY0/...0&linkCode=asn