Small Block LA rocker shaft hold downs

Reading thru these posts are helping me understand some things on my setup. Question, there is a notation that the rockers are clearanced for 340 valve springs.... what’s the difference or spring diameter that the clearance relief is critical. My 340 has rebuilt X heads so not sure what my spring diameter is or if the clearance is important in my case, but can’t let this new to me info slide in case it is important. Thanks, Casey.


Turn your engine over by hand and watch the inside of the spring retainer to see if it clears or hits on the rocker arm as the valve lifts....