These plugs came out of my trucks original 5.3. It has 78,000 miles and runs great. It does not smoke. 7 of the plugs were clean, but #7 had all these deposits on it.

 

That's oil.

 

But how's it getting there? Rings, valve stem seals, valve guides.....?

 

The only way that I know to distinguish between rings and valve guides/seals is when the smoke occurs. Smoke on startup = seals, smoke when decelerating = rings. In your case, I don't know what to do.

 

Wouldn't that be too much buildup to only be from start up?

 

Not if it's been doing it for awhile. Do a leak down test, maybe you'll get lucky and hear a leak. I doubt it though, it would be too small.
Maybe it's time for that LS7 you've been thinking about.

 

This is the engine I just pulled from my truck and replaced with a built 6.0. It's going to be sold, but I've got to make sure it's right first.

Is there any way to test for rings/seals with the engine not in the vehicle? I have no provisions to turn it over fast enough to check compression.

 

OK, I'm reading about doing a leak down test now. I've not done one before. Sounds like what I need to do.

 

Harbor Freight has a dual guage tester for $40, LINK. I think I'll drop by this evening and pick one up.