I disagree with Yellow Rose's statement. Pushrod length indeed does effect the geometry of the valve train. Too short or too long can affect how the rocker contacts the valve tip. Also affects whether you're getting the full cam-lift. There are other factors such as stand height and installed valve height that affect geometry as well, but pushrod length is part of it. The pushrods I had made for the 557 cam measure up excellent for the 590 cam and are being used.