Caution Valve Cover Gromets

A friend of mine stopped by yesterday in his camaro he just got together. He ordered new valve cover gromets among many many many other things. Completely redone and very clean. He failed to notice the gromets were sealed on one end, and put them in along with the breather and pcv valve. He hit the road for athe maiden voyage and got about 10 miles from home, it built up so much pressure. That it blew the back intake to block gasket out. Then it shot oil all over everything and leaked way to bad to drive anymore.. So beware if you change your gromets to see it they flow through, or they need cut out.