100 is pretty damn smooth. The flatness is the important part. ESP around the 'horseshoe' area around the oval hole. That's the most important spot.
If the paper curled up on the edges it can remove more meat there and cause a leak because that's the high pressure area that's going to the engine It has the most load per area and happens to be the thinnest part of the gasket. If you look at my picture, the finish is straight lines. After I've done the figure 8's, I pull it one swipe straight. And low spots will still show a matte finish.
On the cover being ''too smooth'' I can't imagine it would be a problem in this exact application. Technically it's better for the two surfaces to mate to the gaskets so you have a mechanical bond of sorts. After all, that is a gaskets job. If you were to make both sides ''perfectly smooth'', then you'd only have the strength of the gasket to hold it in place (that's impossible BTW)
For what it's worth, that cover pictured above was after my car was stolen. It was ran so hot without coolant that the oil pump welded itself together, locked up, and twisted the bottom off my cam sensor. The gouges were a mile deep and jagged as hell. I started with 60 or 80 grit and stopped at 100 or 150 (whichever I had on hand)
If the paper curled up on the edges it can remove more meat there and cause a leak because that's the high pressure area that's going to the engine It has the most load per area and happens to be the thinnest part of the gasket. If you look at my picture, the finish is straight lines. After I've done the figure 8's, I pull it one swipe straight. And low spots will still show a matte finish.
On the cover being ''too smooth'' I can't imagine it would be a problem in this exact application. Technically it's better for the two surfaces to mate to the gaskets so you have a mechanical bond of sorts. After all, that is a gaskets job. If you were to make both sides ''perfectly smooth'', then you'd only have the strength of the gasket to hold it in place (that's impossible BTW)
For what it's worth, that cover pictured above was after my car was stolen. It was ran so hot without coolant that the oil pump welded itself together, locked up, and twisted the bottom off my cam sensor. The gouges were a mile deep and jagged as hell. I started with 60 or 80 grit and stopped at 100 or 150 (whichever I had on hand)
