Piston Images - Need some info

[LongHorn XC]

Is it common to see the pistons like this? I have done some piston replacements in the past and have not seen the dark brown/black on the side of the pistons like this.

These pistons are out of 2 different sleds, both with ~3000 miles on them. One piston is from a carb engine and the other is from a DI engine. Is the oil or heat causing this. I do not want to disclose the type of oil I'm using, I do not want to start bashing thread.

How often are you other sledders seeing this?
Is it typical?
Is it something to worry about?

I was told that worn out rings are causing this and not much of a concern.

Any advise would be nice. I will now have 2 new rebuilt engines.

Thanks.

 

[AkLogan]

How was compression prior to pulling them? Maybe some blow by going on I think?

 

[mike_s]

I would say that there is some definate blowby there. Could be from oil too. Would you be willing to disclose weather the oil you were using was synthetic or dino or a blend?

 

[RACINSTATION]

The darker piston has blowby. I would not say it is the oil or the engine. I would just say that the piston to cylinder wall clearance or ring end gap is too loose. I have also seen this happen when a new piston is installed in a non honed cylinder.

 

[mtsummitx]

Looks like poor ring seal to me (worn rings). The one on the left looks like it may have experienced some heat, but maybe just ignition heat going by rings as well. My 2 cents.