Piston Damage, What caused this?

[hrhoward]

I tore apart a 1988 3800 and found this on #3.
What could of caused it?

 

[1chance]

Aint no telling?

 

[chris mccord]

I've seen SC pistons chunk the edge of the piston off from detonation. Yous looks like it wore off rather than breaking off. The edges look smooth where the piston is missing. Or at least it appears that way. I wouldn't think and NA would detonate enough to chunk a piston. I guess pull it out and get a closer look.

 

[d90dan]

Is that a big dent in #1, or a reflection?

 

[BetMinesFaster]

Looks like detonation to me!

 

[GNTIM]

Looks like a lean condition followed by detonation. My first guess would be a clogged injector, but there are many other possibilities.

 

[BetMinesFaster]

Lookin at the difference in piston color and the head gasket between the front 2 cylinders im leaning on detonation man!

 

[hrhoward]

While diagnosing a very rough idle I found this:
Code 43-knock sensor bad
Fuel injectors were were badly clogged with rusty bits from a fuel filter that had come apart, especially number 3.

I was leaning toward detonation damage myself. :frown: