Why are my pistoins scuffed?

[Black'95]

Ok, so these pistons had about 6k miles on them. Obviously, cylinder 2 blew up because the car ran low on gas and it popped. The question I have, is why are the skirts all scuffed up? Everything I can find online about scuffed up skirts points to lack of lube, PTW clearances off, wrist pin seizure/clearance issues, and POSSIBLY detonation. I did have issues with meth injection lines popping off, so the engine definitely saw some detonation at times. When cylinder 2 blew the crown off, the headgasket popped, of course.

I am also wondering which side is the thrust side on the pistons, exhaust side, correct? I did not assemble this rotating assembly, so I can only assume that clearances were set properly, but who knows...

Any insight is appreciated; thank you!

Ok, some of the pictures are too large to upload, so here is a OneDrive link to all the photos I took. https://onedrive.live.com/redir?res...24&authkey=!AMxaLHjpwKzfRxs&ithint=folder,jpg

 

[BSSMeclipse]

Id say there is definitely a lack of oil, im not sure how that would be caused sorry im not more help but that definitely not enough lube.

 

[Chumpaumpalumpa]

Jesus Christ. Looks like you knocked like crazy and the cylinder distorted from something and is out of round.

 

[DSMPT]

Too high EGT.. The skirts also started to be melted. That's why the pistons which are less damaged on the piston top have less damages on the skirt.

 

[Hammer_Gaidin]

Making the assumption that your oiling is ok, I would agree with DSMPT. If your gas temps were getting high frequently, they could have caused issues with oiling burning off, or expansion issues. Based on the fact you had detonation issues, this is where i would lean.

 

[motomattx]

Your issue is more than one single problem, your clearances were too tight and or your bore wasnt ever round, you had major detonation issues and you inhaled melted aluminum into all of the cylinders.

 

[Black'95]

Thanks for the replies! As far as the cylinders being out of round, I suppose that's entirely possible. Everything was checked originally with regular ARPs, and then I switched to H11s last year or the year before. I have the meth lines switched to stainless braided ones, so no more issues there.

As far as the high EGTs go... It was blowing the wastegate open (dual blue tial springs ~23psi) pretty bad, so I'd say there was definitely a lot of exhaust pressure and heat. Bad meaning it'd peak at 33psi around 5500 and fall to around 26psi by 7k. If I remember right, I couldn't really raise the boost any higher than that. Maybe I could raise it a little, but it would definitely just taper back off the the same ~26psi at the end.