You gotta see this ......

Back to the adjustable rocker comments. Other than stock cam and valve train, how do you know where the lifter preload is without a adjustable rocker? Tighten the shafts down and run it? Heck with longer pushrods (if you didn't measure to get the proper length) the preload could be at the end of the lifter piston travel. They could be bottoming out inside the lifter causing exactly what is going on here. Those pushrod pockets in the stock rockers don't just break for no reason.