After disassembling the cylinder heads to service the valves and putting everything back together I realized that the upper rocker arms (openers) weren't centered and I had somehow replaced the shims out of order. Getting everything sorted out left me with the exhaust valve on the vertical cylinder not having any shims between the rocker arm and the outer wall of the head. Placing even the thinnest shim between the arm and the case leaves the arm centered unevenly over the valve shim. So, is the shim just a shim and location is irrelevant other than regarding the centering of the rocker arm, or does the shim act as a bushing and one is required between each of the pieces on the rocker arm shaft (i.e each side of the rocker arm and spring clip)? I was also wondering about the torque values for the cylinder head nuts. The haynes manual has them at like 11, 27, and 39 n/m of torque which equates to 29 ft/lbs at the highest value (1ft/lb being equal to 1.3558n/m). They seem ridiculously loose so I was thinking I am making some error in this regard.