Engine - Valves
The Rolls-Royce Twenty and 20/25 engines had a distinctive overhead valve and cylinder head arrangement with a "heart-shaped" or "kidney-shaped" combustion chamber.
Post War Valve Seal Tech Info
A Technical Contribution By Bill Vatter - Georgia.
*Note: For sizes other than these for a neoprene seal on various applications, Bill writes: Botom line, take a packing cover and a valve to the store and root through the boxes until you find the one that fits. There are a multitude of sizes, and any particular store might not have all different ones. Therefore, you might wind up on the phone to Clevite Engine Parts technical consultant to figure this out from engineering specs.
Valve retaining tool holding an intake valve in position (inside view).
Valve parts: Piece of packing string, inner and outer springs, inner spring support washer (and packing chamber cover), compressed teflon packing (after 5000 miles use), valve retaining clip (obsolete; no longer used), outer spring support washer, neoprene valve seal (NAPA # CEP 216-1021)
Teflon packing wound on valve stem ready to be hammered down.
Packing chamber cover in place before hammering
Packing chamber after packing being compressed by hammering. Note the base of the packing cover is very slightly proud of the edge of the outer spring washer, indicating about .020 of height added by the packing, a critical point. Too little and the packing won't seal. Too much and the inner spring will be over compressed, possibly becoming coil bound, which would cause parts to break.
The neoprene seal in place. This seal provides additional oil control, which is helpful when the intake guide is worn. Disclaimer: The long-term effectiveness of the neoprene seal is unproven, and the neoprene seal should only be considered a temporary repair of use until an overhaul including valve guide replacement is conducted. See *Note above.