Valve lengths and head diameters vary from the early unit-construction Triumph 500 models with the “squish-band” cylinder heads to the later models with the revised heads to accommodate the larger inlet valves. This inlet valve is specified for the 1959-1966 5TA and T100 models.
UK-made to original specifications, this nickel-plated inlet valve has a head diameter of 1.430″, stem diameter of .311″, and an overall length of 3.540″. The Alpha reference number is V187.
The inlet valve allows the ingress of the fuel charge to ignite under compression in the combustion chamber. It is critical the valve seat and valve face make a seal when the valve is closed to maximize compression. The valve stem must have the correct clearance within the valve guide to be properly lubricated and minimize oil consumption.
The rocker boxes and cylinder head must be removed to access the valvetrain. A valve spring compressor is employed to compress the springs far enough to remove the retaining collets from the top collars. Once fitted into the valve guide, the replacement valve will require “lapping-in” to the valve seat. Refer to the factory workshop manual for the complete instructions. Replacing valves is a multi-step procedure and may be best done by a professional machinist.
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