nick and i did a 5.3 to 6.0 swap a month ago in my z71, i didnt have a 6.0 tune so i left the 5.3 tune in, it took several attemps to start and fail, after sitting a few minutes and myself getting ready to spend the 100 bux for credits chris went over and it started right up has been running perfect ever since yeah it may need a tune but i bet theres not much that needs to be changed !

 

I'm thinking that if you're getting a loud knock, that is NOT a tune issue. Tuning controls ignition, fuel/air, etc... last I checked you won't get a knocking from the slight variation in any of those differences found between the 5.3 and 6.0 tunes... I mean pinging, yeah... missing, yeah... not running for crap, yeah... but what that a tune controls would knock? I personally can't think of anything, so I vote something is wrong mechanically. The motor needs to be pulled and checked... I read somewhere a guy got an LS out of a rolled truck, mild hydrolock bent one of the rods... perhaps thats what went down on your #3 and 5 holes...

 

A loud knock at idle is not caused by tuning...

Quick question, what happened that you started and deleted 5 of the same thread? (I "physically removed" the 4 other threads for you)

 

phone posting it whent crazy on me . well he got the 6.0 an 4l80 tune on it. nothin is wrong with it there. it knocks at idle an louder when revved. im tryin to c if the junkyard will work with me, even tho its out of warranty. running out of cash at this point an its my dd, thanks for the input so far guys.

 

i was drag racing my 6.0 on the 4.8 tune... so count that out... hahaha...

man this sux... does it sound like it is in the bottom end or valvetrain??

 

Good luck, keep us posted.

 

Bottom end. What could it possibly b?

 

Rod bearing?

Is this the engine that didn't have compression between two cylinders? Is it possible that the head gasket is blown, and coolant got into the crank case?

 

Yea the compression is normal, just knocking now. I was thinking possibly rod bearing also, ima c what the yard says tmmrw n go from there. An im not sure on the head gasket tho, but the mechanic says all is good besides the knock. How expensive/ difficult if the bearing is bad?

 

My guess is it had water in them 2 cylinders that caused rust! Took alittle to clean the rust off & the compression came back up! The knocking is from how the water got in. Maybe they wrecked in the ditch sucking water into the motor! This is just a thought