RT - I'm going to be using 1.645 diameter springs with Comp Ti retainers. The retainers tend to hit before the spring so I'm carefully watching the rocker to retainer clearance. The Comp retainers are about 1.500 inch diameter so they are a little smaller than the OD of the springs. Here is the setup with some checking springs installed. I don't see why the spring would hit before the retainer so I think the 1.645 should clear fine.