mikekantor

iTrader: (5)

I'm preparing my G20 engine for assembly right now. How seriously do I need to clean off the old head gasket?

I removed all the old material, there is just some darker color remaining here and there, but it looks smooth and flat so far.

pmohr

iTrader: (26)

Just because it looks 'smooth and flat' doesn't mean it is.

If it's a nice flat sealing surface then no problem, but if you can actually feel any of the residue, then you need to clean it some more.

mikekantor

iTrader: (5)

Yeah thats been the idea so far. I can't feel any material, but im a noob at this sort of work so I dont have any instinct for it. I'll get some measurement tools and quantify the flatness.

streetzlegend

iTrader: (8)

If it dosnt feel like sliding ur finger over glas then its not clean enough. just dont scrape it with metal or a blade. try scraping with something plastic if needed. get brake parts cleaner on a soft cloth, spray the cloth and whipe.

Matt93SE

iTrader: (44)

Get a metal straightedge and lay it across the block.
if you have a piece of square metal tubing, take it and wrap it in some 400+ grit sandpaper and run it across the top of the block. you'll find the high spots.