StolenFox

So shortly after I picked up my junkyard LQ4 a good friend of mine gave me a complete LY6 that his shop replaced in a fleet van. The engine spun a couple rod bearings and was done. Great news because now I've got the L92/LS3 style heads and intake for my LQ4! Thing is, I'd like to know what happened here so I can learn from it. First, backstory on the LY6: It came into my friends shop with a flat lifter (the roller was ground half away) and damaged cam so they put in a new GM cam, cam bearings and lifters and returned it to the customer. Van made it about 5000 miles before the spun bearings.

Now the things I've discovered while tearing it down: Every intake valve has struck its piston. Not hard enough to visibly bend a valve or damage the tops but definitely left marks on the pistons. The cam sensor has been ground down about 1/16 by the phaser. Doesn't seem like the phaser moves like it should but I've never actually held one prior so not exactly sure what I'm looking at.

I understand that the trash from the lifter and cam eating each other could have put the hurt on the bottom end from the get go and it was just a matter of time. My question is how could a stock motor have PTV clearance issues? Can the VVT phaser get stuck in the wrong position and allow the pistons to hit the valves? Could the dealer have provided the wrong VVT cam and it had too much lift? How could the phaser thrust towards the cam sensor enough to grind it?

Educate me fellas!

Thanks,
S.F.

LLLosingit

iTrader: (4)

They never should have replaced just the cam and lifters, They wasted the customers time and money. All the metal from the cam and lifter was circulated through the engine and it should have been torn down then cleaned and rebuilt. I would guess that the metal destroyed the main/rod and cam bearing adding even more metal to the problem. The cam phaser is controlled by oil pressure so it's possible that it was stuck in the wrong position. It's also possible that when it ruined the bearings that it allowed the piston to travel further into the bore.
If you plan on using the engine I would make sure it gets cleaned and flushed thoroughly. If you plan on reusing parts I would make sure they aren't damaged. I would even go as far as disassembling the heads and checking each valve and cleaning everything. The metal would have gone through everything from the push rods to the rocker arms to the seals and possibly the valve guides.

Did the cam retention plate show wear also? Many times the cam is pushed around when they are being ground down by a lifter.

StolenFox

The customer wanted the "band aid" route, obviously not a wise choice. Pulled it the rest of the way down today. Crank is done, 1 rod is done, all bearings show contamination damage. The backside of the phaser is not worn however the bolts that held it in place were siezed in place and one needed the air chisel to work it loose since the torx socket in the bolt head stripped out. I'm almost positive the phaser is stuck in place as well.

So I ended up wit a rebuilder block, the covers, the 823 heads and intake. The rotating assembly is hitting the dumpster...

S.F.