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When you install an aftermarket camshaft with more valve lift than stock, the factory valve springs aren't strong enough to close the valves fast enough at high RPM. This causes 'valve float' — the valves bounce open when they should be closed, which can lead to catastrophic valve-to-piston contact. Comp Cams' beehive springs use a progressive rate (softer at the bottom, stiffer at the top) that controls the valve precisely while putting less stress on the valvetrain. This kit includes springs, retainers, and locks for all 16 intake and exhaust positions. This is NOT optional with an aftermarket cam — it's mandatory.

The factory HEMI has MDS (Multi-Displacement System) lifters that can collapse to deactivate 4 cylinders during light driving. These MDS lifters are completely incompatible with aftermarket camshafts — the cam profiles will cause the MDS mechanism to malfunction, leading to lifter failure, collapsed lifters, and engine damage. Non-MDS lifters are solid hydraulic rollers that follow the cam lobe faithfully without any deactivation mechanism. If your Challenger has an automatic transmission, it has MDS and you MUST replace all 16 lifters when installing an aftermarket cam. Manual transmission models already have non-MDS lifters.