Cork gaskets suck. I wish I had never used that thing. The cork is spongy and is constantly changing thickness. They require very low fastener torque, so the bolts won't stay tight. I was constantly noticing a leak, and had to retighten the bolts, which would stop the leak for a while, but it would come back. The OEM assembly just uses RTV to seal the cover. Okay, rant off on that.
I decided to try one of the Felpro rubberized reuseable gaskets. First I removed the air cleaner, pulled all the vacuum lines that crisscross the valve cover, carefully marking each one, and removed the fuel line from the filter and swung the line away. Remove the air cleaner mount and the air pulse relay set from the valve cover. Then remove all 15 valve cover bolts.
Then pop the valve cover off and remove.
Scrape all that old gasket off the head. Be careful to keep it out of the head gallery as much as possible, but you're probably going to lose some of it down the pushrod ports. I used a razor sharp woodworking chisel to clean the head, but don't leave scratches. If you doubt your chisel skills, use a plastic scraper.
Clean the gasket off the aluminum cover. Pull the vent risers and clean all the carbon out of those. Mine were not plugged, but some will be and your PCV/CCV won't work right if they are clogged. You can see the Felpro rubberized gasket in the background.
This is NOT cleaned yet. All that old gasket gunk has to be completely cleaned.
I used a bottoming tap to clean the threads in the head. They are 1/4-20 threads.
This is where it gets interesting. On each end of the head, I found this mill decking error. That's about a 5-10 thousandths mismatch left by the mill cutter. Too much for most gaskets to perfectly seal. It was worst on the rear, but some across the front end too.
To make matters even more interesting, the valve cover die casting left these divots spaced around the sealing surface. Those are around 10-15 thousandths deep too. I think they might be the mold fill risers, but not sure. Anyway, they are right across where the rubber gasket rib lays, and I'm sure they would leak.
Of course there is one right in the center of the rear of the cover.
I put a smear of RTV across the lines in the head, and a small dollup of RTV in each of the cover dimples. I'm sure those imperfections are not an issue with the OEM RTV seal, but the rubber gasket would leak at those points.
The Felpro rubberized gasket has a metal body with spacers at each bolt hole. So when you tighten the fasteners they will stay tight. It's an impressive gasket and well worth the $35 IMO.