The installed height can vary depending on how much the seat has been ground which makes the need for more shims under the spring to maintain the correct height. If the seats have been replaced that could also change the installed height. Another possibility could be the valve spring retainer hitting the top of the valve guide. I had a BB Chevy that I did 30 years ago and didn't check clearance between retainer and top of guide. I broke a number of roller rocker arms and bent pushrods before I figured it out. In my case the camshaft I installed had a significant amount of lift over the OE cam and that caused the clearance issue. It could be the wrong guide installed or the guide not installed properly. Just a couple ideas. Don
