Pitting in Cylinder?

Hey guys,

I have a GM 3.1L that had a head gasket go on cylinder 1. It was allowing coolant into the cylinder when it cooled down at night. Fortunately, there are no signs of hydrolock. Unfortunately, when I pulled the head, I found dark marks on the cylinder wall. I tried to rub them away, with no luck. The cylinder wall itself feels slightly rough where the spots are.

Does this mean I need to pull the engine? It was running & not making any noise or blue smoke before I pulled the head, and the head had decent compression.

Here's a picture:

https://imageshack.com/i/eycBL1TUj

To me, that looks to be a bit of flash rust.

Unfortunately, if you want to do a proper repair job and fix it right, you may have to pull the engine and get it machined out. You *might* be able to sneak by with just a re-hone and some fresh rings, but that's being pretty optimistic.

If you just want to slap the engine back together for a couple months and then get rid of it, you would probably be ok as long as it's pretty smooth, but for anything long-term, I would definitely machine it out properly. Every time the rings go past the rough spot, they will wear down more and more, which would cause more problems in the future - mainly blow-by from the worn rings.

My $.02.

As rust goes, thats nothing. If this were my engine, I would grab my home and hone the cylinder, lightly, just enough to get rid of the worst of the rust, then put it together and drive it.

If no hone is available, I would use some 400 grit sandpaper, with a bit of oil on it and sand down the rust areas a bit, then reassemble and go.