The passenger valve cover on my father-in-law's '99 Expy cracked so I'm replacing that right now. The challenge I have is getting the valve cover back on without the gasket falling out. Is it OK to use some black silicone on the VC to tack the gasket into place, or is that going to cause leaks?

 

It should be ok. Just use small dabs near the bolt holes and let it set up for about 20-30 minutes and it should be fine.

 

x2. you should be ok with what LxMan says.