998/1049 Shim in tappet, lightweight valve spring kit, titanium retainer
KPMI® shim in tappet systems locate the adjustment shim in the hardened steel of the tappet body, where it is impervious to wearing (ovalling) and kicking the shim out. By designing the tappet and retainer together as a system, the shim couterbore depth in the tappet has been maximized. This allows for increased insurance against losing the shim even in the event of valvetrain separation during severe operating conditions, over-revs, or extreme boost pressures.
This is the kit we recommend for racing applications, or trail guys using antilag. The shim in tappet system is the absolute best way to ensure your valve shims stay put during antilag application or hitting the rev limiter and inducing valve float.