M-8 Dual Spring Rocker Shim Conversion System
The innovative design of these new rocker shim conversion system kits (for dual spring applications) from Pacifica, California based Kibblewhite Precision Machining (KPMI) add a 09.5 mm hardened steel shim between the valve tip and rocker arm to increase the allowable rocker wipe area for maximum valve lift (up to 0.675" valve lift compatibility).
Offered with either titanium or H.T. steel retainers, the kits include heavy duty 9° H.T. steel keepers, 09.5 mm steel shim, red Viton seals and utilize a dual spring system and a lightweight retainer that houses a standard Ø9.5 mm hardened steel shim.
The rocker arm rides directly on the shim surface. The significant increase in the allowable rocker wipe area created by the 9.5 mm diameter provides the ability to utilize larger lift cams - cams that were previously unable to run on a 6 mm valve stem.
The adjustable system allows for at least 0.060" of spring shims, tailoring the pressures and lift capacity to meet the engine builder's needs. The rocker shim thickness can be varied to adjust effective stem protrusion.
The performance engineers at KPMI strongly recommend running titanium valves for maximum performance when larger camshafts are used (and valvetrain acceleration values increase) and advise shortening the valve stem tip ("tipping").
There will be an anticipated increase in effective stem protrusion of approximately 0.100" with the use of the shim and the system must be run with KPMI's newer style M-8 valve guides, which are shortened for 0.675" valve lift.
KIBBLEWHITE PRECISION MACHINING
