Had brownish dirty crude in my water reservoir, noticed driblets of water coming from the muffler tailpipe. car had a minute miss. Going to replace both head gaskets. What I do not know are the exact steps in adjusting the tappet clearance when I reassemble the heads, and manifolds. The manual does not appear to be precise as how to do this, and I heard different versions. 1997 ford Taurus gl, v-6 3.0 liter. Thank you