Briggs and Stratton Intek Plus 18.5HP How Flat does the head need to be for copper gasket?

[Auto Doc's]

I say don't overthink it. It's not the space shuttle. Sand the surface to true it properly, spray the gasket with copper coat and let dry, then reassemble. Copper in the oil might be minor initially from the copper coat spray on the edges of the gasket. There is really no other copper in the engine itself.

 

[slomo]

Old post but.....

Yes gentle circles or X patterns. Let the paper do all the work. Do not push with any force on the head or block area. Use your open fingertips while holding the head. Open fingertips are two ways to lower contact pressure. Really warped ones I start at 220 grit wet/dry paper. Once the head starts to move smoothly, progress to 400 grit. Initially the movement will have a slight dragging feel. Soon it will be smooth to push. Progess to 800 to finish her off.

Spray the gasket both sides with the below juice. Do a triple torque rotation on the bolts.