We have been working to repair a blown head gasket on my son's stock 94 Z28 LT1. We found a small defect in the cylinder wall in the same cylinder where a small piece of the metal ring on the head gasket was missing. I am guessing that the gasket piece got pulled into the cylinder and ended up making the mark on the wall.

The defect is about 5mm across. It doesn't *seem* very deep, but I can feel it with my finger and my fingernail will catch on it if I scratch across it.

What might happen if we just left it as-is? What options are there for repairing it?

I appreciate any suggestions. Here is a photo of it... the defect I am speaking of is right near the center of the picture.

 

Take some sandpaper and lightly sand it down...i would place a shop towel with grease under it to catch the sand that might fall. I have seen that type of thing before with over heating and one that i recently worked on got so hot that the rings were damaged and left that type of thing all over the cylinder, it was aluminum from the piston that was stuck to the cylinder wall... I pulled out the piston and lightly sanded the cylinder wall, then honed the cylinder and measured to ensure that the cylinder wasn't out of round, then put a new piston and rings in.

 

I would not do anything with it unless you think you dropped something that caused it. Anything you try with an assembled motor can cause problems. My fear would be "IF" it was cause pc of headgasket ring then what does the ring look like? If the ring is damaged that will cause problems pretty quickly. The only real fix for the cylinder wall is to bore out the cylinder. I am not sure the would clean up tho. I do not think that was caused by the head gasket ring but it is possible. Looks to me like a casting defect.

 

Not a casting defect for sure...but if you don't take out the piston to check the rings then you might be back in it again. If you put it together and it is missing you will discover with a compression test that you have no compression in that cylinder. Then back in you will be. When head gaskets blow they usually do not make it into the cylinder....so that is why I was trying to plant a seed, and tell the story of the rings that get so hot from overheating that they butt up to one another and break...often topping a piston but not always, sometimes just breaking a ring land, and that is definitely worth checking. I would pull out that piston if it were me.

 

Hmmm, I thought I saw a.... Is that a crack at the point, or just another line in the wall? If there's a crack there, it can keep traveling.