There is a interesting thread about these on the Inliners site. One of the gentlemen indicates the pushrod hole through the head needs to be elongated to allow the pushrod to align with the shorter rocker arm.
The Inliners blurb (informative and knowledgeable) says the directions with the rockers indicate it is a "Install and Adjust" situation. A increase of 5 hp is said to be gained on a 216 by using these item's.
Stuart
