You didn't say if you were using a hyd, solid or roller cam. Lets says you are using a solid. I'm reaching for straws here but the Barton/Trend tool steel lifers are made to hydraulic length. This raises up the lifter cup around .200". Would this help you? I'm not sure. I've put together a few of these Victor Jr. motors and they always fit for me but I'm using Stage V rockers. YRMV. I know it's a reach. Makes me want to go home and mock up another one I have and see if I have the same problem.