The head off my engine is off being Skimmed... should get it back tomorow....

What is the best way to clean the top of a steel block so that the new head gasket has the best surface possible to seal against?

And should I clean the carbon flakey ring from around the very top of the cylinders.... if so, what is the best way of doing this? A screwdriver and or course sandpaper would do it... but perhaps not a good idea? (Pistons are still in the engine, and the engine is in the car!)

[Edited on 25/7/10 by tegwin]

Gasket scraper to clean the top of the block.

The way I've heard of keeping crap from going down the cylinders is to run a thick bead of grease around the circumference, then scrape off, hoover up the loose bits, and wipe it out with a rag. Never tried it though!

best cleaning stuff in my opinion is scotchbrite (the purple if you can get it) with WD40. The grease trick is good, no need to leave a ring on the pistons that was the old fashioned way.

It's sooooo tempting to get a block, slap some 100 grit wet 'n' dry on there and sand away. Problem is, you make grinding paste which is hard to keep out of the pistons and rings. The other thing you do is lower the metal around the edges (where the gasket is under most stress near the bores) so just scrape it clean with a hoover sucking at the same time.
I rotate the engine so that the piston is TDC (on the cylinder i'm cleaning next to) and put some grease on the joint as mentioned above. Clean off when finished, wind the piston down, then clean again. White spirit or summat similar is just the job. Flush the coolant too.

Scrape using back side an old hacksaw blade or use scrapers like these:

I've always used a Stanley knife blade with a couple of strips of duct tape on the top to stop it digging in to my fingers. The grease trick works.

nice flat oil stone or diamond stone keeps it flat and as said grease is good
regards
Paul