I'm putting a new head gasket on my wife's Volvo. Looking for input on just how clean the top of the block should be before I put the head back on.

This is how it looks after 30 minutes of using a cotton rag with some brake cleaner on it. There are areas of discoloration that remain. In one small area, I used a razor blade perpendicular to the block, but with light pressure, the surface didn't get any cleaner.





Anyone think I need to go further? Suggestions on a non-abrasive to use?

 

I use 800 grit 3M sandpaper and I wet sand it by hand. Probably not supposed to but it's how I've been able to get graphite gasket material off the Honda blocks and heads without taking any significance of material.

The other thing I've heard used a lot that works well is the highest grit (120 I think) you can get for the rubber fingered roloc discs. I think the white ones.

 

I may try that TomCat. If I just stuff some paper towels into the bores, am I protecting the bottom end enough from any debris getting in there?

I did some reading on those fingered roloc discs and I'm worried they may do more work than I want.

 

That block surface prep looks good, hit the head gasket with copper spray if you are concerned. I would not sand and never roloc any gasket mating surface, asking for low spots, asking for trouble.

 

If you can get a low spot by wet sanding with 800 grit 3M wet sandpaper, then you are going WAY too hard. I also used a block. But the real bad spots of graphite I had to do a focused wetsand.

As for the fingered roloc's, the highest 120 grit (white ones) is what many shops use as they flex and don't remove material like traditional roloc's.

I did see someone use a piece of glass to sand a head, a ghetto resurface job, I still would only use a real high grit sandpaper and still would wet sand, taker forever to remove any significant material but it would be flat.

And yeah I put wads of paper towel into the cylinders to catch the water. Then wiped the lips when I was done. The rings don't go to the top of the deck so never even see any grit if it drools over into the towels. 3M makes high quuality sandpaper so very little grit comes off and it's just wet sanded material drooling over.