After lifter preload adjustment, which screw is used to lock the setting?

• A. Polylock
• B. Locknut
• C. Dowel Pin
• D. Cam Gear

Answer: (A)

After dialing in lifter preload, you need a reliable way to keep that setting from shifting during engine operation. A polylock is a dedicated locking screw that threads into the rocker arm and clamps the adjusting screw in place. When you tighten the polylock, it locks the preload by applying pressure to the adjuster, so the setting stays put even under vibration and heat. This makes it the preferred method for securing preload in performance valve-train setups. A locknut can work but is more prone to loosening with vibration, while a dowel pin or cam gear isn’t involved in locking the preload.