Pitted Piston Heads
 

So, I bent a rod and am in the process of getting the engine rebuilt. I have some pitting in the top surface of the piston heads (two are worse than the other two) and no one knows for sure what would cause this. There’s no damage to the head or valves so it’s unlikely that something got sucked into the intake. Could this be because of my tune? I’m getting a pro tune with the rebuild to be on the safe side. We would just like to know if anyone has seen this before and knows something we should be watching for regarding the hardware.

http://i1258.photobucket.com/albums/...5/1511be03.jpg
http://i1258.photobucket.com/albums/...5/c2515b43.jpg
http://i1258.photobucket.com/albums/...5/aa91efcd.jpg
http://i1258.photobucket.com/albums/...5/a2ceaff9.jpg

I open the floor to the more experienced of the forum.

Possibly pertinent information: I was running a tune that I evolved over several iterations using Abilor’s Tuning Guide, based on a Cobb stage 2 map. I was targeting 19 psi boost on stock internals but with other supporting mods (see sig). MAF cal was verified (repeatedly) and I had been running this map for close to a year. I had not touched the timing, but there’s a known issue with the VVT on the MS6. There was no other catastrophic internal damage to the engine. The block is getting bored out 20/1000ths for some scoring on the #2 cylinder wall. Just bought the hardware for the rebuild and waiting for delivery.

Bonus pic:
http://i1258.photobucket.com/albums/...5/5e4ff31c.jpg

There is a lot of carbon build up on pistons that appear to be pitted. Is the pitting actually in the metal or in the carbon? The most logical theory would be something got into the combustion chamber. Is there any damage to your turbo compressor?

yeah, that doesn't look like the pistons are pitted, just the carbon buildup on the top of 'em starting to break off.

btw, nice organization on the cam caps, lmao.

@Auburn: I'll see if I can get another look at them this weekend. I didn't think the carbon was thick enough to chunk off like that, but it may be. An OCC is going on with the rebuild. I have not looked into the turbo, but I will.

@chimmike: Yeah, that was the dealership taking everything apart, trying to get warranty coverage. Took everything in pieces over to my budy's place for the rebuild.

Did your spark plug insulators crack? Something got loose in there. Its weird that its mainly around the far edges of the valves.

Those pistons are way too clean for a DD, how many miles are on it?