Rebuilding an Engine that doesnt need a rebuild.
 

There is a strong possibility I will be scoring a 4.0L Jeep I6. It has 190K miles but still smogs and runs like a champ.

But Id feel silly installing it without freshening it up at all, so, what are the high wear parts in a motor? Im thinking, new valve guides in the head (skipping the valve job), flex hone the cylinder and new rings, new crank and rod bearings, and a new timing chain.

Anything else? Im sure the lifters and bores will be fine, machine shops dont really even touch the lifter bores. But how about the cam bearings? I would think that they dont wear out nearly as fast since there isnt much rotating mass on a cam.

AND if anyone plans to lecture me about doing it once and doing it right, please also answer my question :) :p

Lap the valves and install new valve springs.

Think the valve seats will be fine? Its an iron head. Can you get a tool to lap valves yourself?

Yes, you can pick up one of the cheap suction cup style ones at any autoparts store as well as the compound.

Thanks man. Whats your experience with cam bearings? Have you ever really seen them wear out?

Look at the lifter and rocker components. The rocker bridges might be twisted like mine were.

I think the 4.0 motors are prone to valve issues. The valves stop rotating in the guide, causing abnormal wear. We pull the rockers and look for scoring on the valve tips. Not sure what years are effected, but there is a factory TSB.

You can use a hose that can fit on the valve stem as well and just pull on it and twist.

See it in action here. Just skip to about 13 minutes.

Thanks for that video! It's great. I didn't realize that lapping valves meant checking them. I thought it meant taking off material to make the edges true again. Good to know. ...So if they seat correctly, no need to machine or replace anything.

I have an 88 4.0 long block with intake and exhaust sitting in the shop...I want to get rid of it..std bore was running when I pulled it.