Salvaging a L86 6.2L V8

CadillacLuke24 · May 18

2015 Silverado LTZ Z71 6.2L L86 V8.

Last fall my cylinder 2 valves decided they have enough and did a little tap dance on the top of the piston. The most cost effective option was replace the engine. GM did not have a reman unit available, so I found a new GM engine at Michigan Motorz, a marine engine shop in some state that starts with an M. Seeing as there was no core charge for my new engine, my old one is under wraps in my storage unit.

Seeing as spring is finally here, the weather is suitable for long periods of activity in an unlit storage unit with no power. At the best I have a rebuild project, at the worst (and most likely) I have a new coffee table base. The Cylinder 2 piston is cracked, the valves are clearly shot (not that they would be reused in a rebuild), and there's obviously concern for metal in the oil. In the spirit of not ruining a rebuild, what should I toss? I've heard the intake is contaminated, and others have suggested the cylinder 2 injector is a no go. I'm thinking the VLOM is toast, likely the even bank cylinder head, and the vacuum pump (though that's the old design and would get scrapped anyway).

Suggestions? Thank you for your time.

newdude · May 18

I'd be checking the rod and rod bearing on that cylinder but also, tear it down, check all the other bearings and the crank. If nothing is scored from metal running through everything, new piston, valves, DOD delete it and upgrade the valve springs.

Edited May 18 by newdude

Grumpy Bear · May 18

I lost track of Clyde when it passes 200K. No idea how many miles are on it. Perhaps Luke would fill that blank in?

1 hour ago, newdude said:

I'd be checking the rod and rod bearing on that cylinder but also, tear it down, check all the other bearings and the crank. If nothing is scored from metal running through everything, new piston, valves, DOD delete it and upgrade the valve springs.

Question @newdude. You would replace one piston with zero-cylinder prep assuming no scoring naturally? I know GM does this on motors up to 150K when doing warranty work but is it effective?

BB68 · May 18

Tear down and inspect all parts?? Send what you find "good" to machine shop for further evaluation.

I will bet that you will find terminal block damage in that cylinder... minimum of a sleave in #2. just my experiences with dropped valves.

CadillacLuke24 · May 19

Definitely going to do a full teardown and inspection, that's half the fun.

Yeah I'm not optimistic about cylinder 2...this may be a spare parts source more than anything.

Engine first developed symptoms at 252,030 miles (persistent misfire, related code, MAP sensor code, and inability to run relatively smoothly at idle). Engine gave up the ghost at 252,062 miles (stalled and would not refire) and was removed at 252,064 miles (got tugged to the dealer).

Grumpy Bear · May 19

So, how many miles are on the new motor?

What fun, starting all over again.

KARNUT · May 19

4 minutes ago, Grumpy Bear said:

So, how many miles are on the new motor?

What fun, starting all over again.

I’m wondering where that engine is going if rebuilt. At 250K and a new engine that should be the last engine.

CadillacLuke24 · May 20

New engine has 16k miles and is doing well. Recent fuel economy is right around 20 a tank. Quite pleased. I was able to do a much more proper break, with a 55 mph speed limit and 3000 rpm redline, as well as an oil change immediately following completion. That is the one bright spot, I have been able to get a much more detailed break in completed.

That's good question Karnut, I did not see this coming, though now that it has happened, and I may have a spare, I may make a spare. Rest of the truck is in exceptional condition for the age, and resale is not a concern. If this happens again, I may wash, rinse, and repeat. Sure, things wear out, but with proper care I can slow the aging to a crawl.

KARNUT · May 20

1 hour ago, CadillacLuke24 said:

New engine has 16k miles and is doing well. Recent fuel economy is right around 20 a tank. Quite pleased. I was able to do a much more proper break, with a 55 mph speed limit and 3000 rpm redline, as well as an oil change immediately following completion. That is the one bright spot, I have been able to get a much more detailed break in completed.

That's good question Karnut, I did not see this coming, though now that it has happened, and I may have a spare, I may make a spare. Rest of the truck is in exceptional condition for the age, and resale is not a concern. If this happens again, I may wash, rinse, and repeat. Sure, things wear out, but with proper care I can slow the aging to a crawl.

I never had a problem keeping my vehicles looking and performing like new. Even my work trucks going up and down ROWs. With the prices of new ones the incentive is there for rebuilding.

BB68 · May 20

On 5/19/2023 at 2:14 AM, CadillacLuke24 said:

Definitely going to do a full teardown and inspection, that's half the fun.

Yeah I'm not optimistic about cylinder 2...this may be a spare parts source more than anything.

Engine first developed symptoms at 252,030 miles (persistent misfire, related code, MAP sensor code, and inability to run relatively smoothly at idle). Engine gave up the ghost at 252,062 miles (stalled and would not refire) and was removed at 252,064 miles (got tugged to the dealer).

Yes seeing the carnage is pretty interesting/satisfying.

I used to part out 6.0HD pickups. Usually they have a bad trans or Tcase. The last one which had the least amount of miles of all of them had "reverse out" for years... then the farmer said it finally stopped moving forward. Ok I didn't even ask about a 6.0ls.. made normal offer... brought home to start up after 5 years of sitting, engine has zero oil psi and a rattle. I think ok bad sensor possible bad lifter, I'll check with manual guage. Installed my snap-on psi gauge - zero ... At this point I know I'm not rebuilding and just parting.. Get the engine pulled and then take the pan off. It had a broken rod!!! And on top of that the quarter rod still hanging off the crank came around and punched a hole in the main oil galley... thats why there was zero oil psi. How a 6.0 with a ecu rpm limiter in a completely stock pickup can break a rod I'll never know. Just look at every turbo ls build on the internet with junkyard LS's

JONBLARC7 · May 23

I just rebiult my L86 alittle over a year ago. It already had head cam from and stuck lifter. Then rod bear 1 and 2 ate them selfs. Now it's heads cam forged pistons.

1. I replace radiator because it shares the oil cooler. And oil cooler lines

2. Oil pump and pick up tube, If you pull the pick up tube out of the pan the new one needs to be press in at the machine shop. Learned that the hard way.

3. Deleted vacumm pump it was fool of metal.

4. lifters and trays even though they only had 50K miles on them.

5. machine shop clean and assimbled the short block with new bearings, crank, and pistons. Reused 6 of the old rods. They only charged 500$ bucks for labor and it was well worth it.