Hole in cylinder 1 piston

[JayH]

I bought an 02 yukon xl in pretty decent shape except the engine. The owner said that he heard clunking in the drivetrain, and it chugged to a stop. His mechanic tore basically the whole front end of the engine off, everything but where the issue was and just told him, he'd need a new engine. So I got it for $700 which is what I'd get to junk it, so no money lost. Anyway, I began tearing into the engine, I took both side valve covers off, and the driver side looks good, but the passenger side, the first cylinder from front to back, the valve spring broke, and the valve sunk down into the valve seat. And when i turn the motor over, it stops at a point. Long story short, I removed the passenger head, and found the bigger of the two valves snapped off, upside down in the piston. It was actually pretty funny. So I figured that the engine is toast, or at least that piston. But i was able to wiggle the valve bottom loose and it popped out. When I did that, the indents in the piston appeared to not have gone completely through. I put a little bit of oil in the indents to see if it'd leak through, and it didn't, just pooled up. So my question is, is it safe to get the heads machined, and new gaskets, and button everything up? Can I get some sort of high temp compound to seal up the indents, or am I still toast and will need to pull the engine or the piston at the very least? I'll post pictures when i get them from my phone. Thanks

 

[JayH]

Here are some pictures, sorry for so many.

 

[SnowDrifter]

Rebuild time

 

[iamdub]

Definitely can't use that piston. Aside from the metal being fractured (regardless if it is liquid-tight) which means it would likely crack and shatter soon, that indent would be a hell of a hot spot leading to detonation which would surely shatter that piston. If you insist on running that motor with the bare minimum, replace the piston and fix or replace the head. I'd only entertain the thought if it was a low-mile engine with otherwise perfect numbers (compression, clearances, etc.) and if I wanted to invest as little as possible. Otherwise, replace it with a good pull-out or rebuild it.

 

[JayH]

It has 225K. The plan is to get it road worthy and get another motor from the junkyard that the boy and i will tear down and rebuild as a project. Would it last a year at least if the piston was replaced?

 

[SnowDrifter]

Maybe, maybe not.

You're at this point, why you going to insist on doing the work twice?

Metals in engines are more sensitive than you'd think. The shock from the impact could have tweaked the rod slightly, forming a weak spot that will fatigue over time. I mean... You need to be careful how you store parts on a shelf just because they can distort over time.


I really wouldn't half ass this one.

 

[Scottydoggs]

when the piston gets stopped like that the rod bearings take a beating, likely fail before the piston would. crank could also be damaged.

 

[iamdub]

X2 to both of the above. The chance of it still failing is greater than the time, effort and money involved to patch it with your fingers crossed. I see ~100,000-150,000 mile Gen3 motors around me all the time for $300-$500. Most are engine/trans pull-outs for well under $1,000.

 

[JayH]

Wow thanks, I'll start looking for another motor then

 

[JayH]

I found a motor with the 6.0 heads on it. I know that without them being milled, i'll lose compression from what I've read. Since this will be an everyday truck, and it comes with the intake and heads, both 6.0, other than compression loss, will the motor suffer using stock 6.0 heads and intake on it? And also will my 5.3 harness plug and play to this intake? I have my intake, injectors, and rail if not. Thanks