Combine all three of these matched parts for an even more discounted price. The stage 1 kit is a complete "drop-in", meaning no machine work or additional parts will be required for stock heads and valves. The Stage 2 and Stage 3 kits come with beehive springs, matched chromoly retainers and locks and are to be used with Boport or other .400 or .450" tip length valves to ensure proper installed height and mechanical clearance in stock heads.