piston scarring

[jimbear84]

Upon disassembly of my engine, I discovered that the #5 piston has some scarring.
What happened?

[jimbear84]

There's also some scarring on the head as well.

Am I going to have to buy a new head now?

[t.mcginley.jr]

You will definitely need new pistons.

From the pic of the head though I can't tell how bad it is. It looks like the edge is all messed up, in which case I would say yes you need a new head. You can grind it smooth again, but there's a possibility of it leaking past the head gasket. Try cleaning it up with a scraper or fine wire brush first to see what the metal looks like and take another pic.

[t.mcginley.jr]

Also just so you know, NA heads aren't too expensive at all if you buy a used set. You may have to clean them up a bit and change the valve stem seals but otherwise they should be good to go unless they have REALLY high miles.

[jimbear84]

Ok, thanks. As soon as I get home, that's the first thing on my list. I'll post the pic when I'm done.

[jimbear84]

So here it is.

And here's the piston.

[t.mcginley.jr]

Definitely looks like either detonation happened or a bad head gasket, or both. The bad news is that the pitting is right where the sealing/fire rings on the headgasket are so there's a good chance it won't seal properly if you reinstall as-is. If the pitting was in the chamber itself you could smooth it out and be fine, but on the edge is different. If you really wanted you could have the heads decked, but the pitting looks too deep for that (a shop would have to measure it).

It would probably be cheaper to just pick up a new head or set of heads, especially since they are just NA heads.

[Extreme Dimensions]

Definitely looks like either detonation happened or a bad head gasket, or both. The bad news is that the pitting is right where the sealing/fire rings on the headgasket are so there's a good chance it won't seal properly if you reinstall as-is. If the pitting was in the chamber itself you could smooth it out and be fine, but on the edge is different. If you really wanted you could have the heads decked, but the pitting looks too deep for that (a shop would have to measure it).

It would probably be cheaper to just pick up a new head or set of heads, especially since they are just NA heads.

This all the way. if you try and re-use the head you will leak through the gasket, and end up doing more damage.

[NolimitZ32]

Kind of looks like the heads have been previously decked and taken out od tolerance. A piston shouldnt be making contact with the head on a spec'd engine and I would think knock would do more damage to the rest of the chamber. Just my 2cents.

[z32loverboy]

Yeah new heads all the way. they're not super expensive and will save the motor in the long run.

[solaire]

Looks like you may have had a piece of carbon or maybe a broken spark plug tip in there at some time that got jammed up in the side of the combustion chamber that finally worked its way out over time. I'm sure it made hell of a noise when it was in there. Does the car have cats? If so there may not be much left in them now unless it went somewhere else. Either way put another piston and a head on it. How is the block side? It may need to be bored if it's got the same damage.

[z32loverboy]

Shoot, forged pistons and bore it over anyway. Make a few more ponies and a lighter rotating mass. Machine work isn't too super expensive