Alright so basically, I found an d16 vavle cover that I'm refurbishing. As I was taking out the old degraded spark plug gaskets, I ended up scoring the area pretty good and was wondering if I could sand the area down and if so, with what/up until what grit to use.

 

Smooth any material that is sticking out... and if you still have any deep gouges in the seal pocket, you can use a small film of honda bond on the gouged area just before installing the new tube seal. Sanding may make the opening too big and thus, may allow the tube seal to fit loosely and leak at best... fall out at worst.

 

Agree: Remove any burrs, then fill any problematic scores with a sealant. Sanding risks opening up the area too wide and/or deforming it so it is no longer a perfect circle to create the seal. Good question to ask though before it's too late.