I finally got around to replacing the valve seals on my B18C1. I'm following WildoutWhite GSR's tutorial that's posted on several sites (such as Team-Integra). I would copy and paste a link but I can't on my current browser. Anyway, I'm stuck on step #14. I just removed the cam shafts. What's the purpose of connecting an air compressor to the spark plug hole? Is this necessary? This step is right before removing the valve keepers. Thanks for any help!