Elgin Z28 Style Valve Springs, Retainers & Locks sb Chevy 400 350 327 305 283 (Spring Kits) All Elgin Products springs can handle up to 0.50" maximum works great for stock, towing and most mild performance cams Spring: Outside Diameter: 1.260", Inside Diameter: 0.785" Closed: 114 lbs. @ 1.710",Open: 318 lbs. @1.210"