Looks like you will have to remove the engine from the SHO to get access to do the work, because you have to first remove the camshafts and valve tappets to get to the Valve Spring, Retainer and Seal.
BTW, there aren't any roller rockers in this system.
QuoteThe valve train uses Direct Acting Mechanical Buckets (DAMB). The camshaft lobes are positioned directly above mechanical buckets which are positioned on top of the valves.
Valve Clearance Check Remove the valve covers. For additional information, refer to Valve Cover — LH and Valve Cover — RH in this section.
NOTE: Engine must be at room temperature before measuring. The valve clearance must be measured with the camshaft at base circle. The engine will have to be rotated with the crankshaft pulley bolt to bring each valve to base circle.
Use a feeler gauge to measure the clearance of each valve and record its location. A midrange clearance is the most desirable:
Intake: 0.15-0.25 mm (0.006-0.01 in)
Exhaust: 0.360-0.460 mm (0.0142-0.0181 in)
NOTE: The number on the valve tappet reflects the thickness of the valve tappet. For example, a tappet with the number 3.310 has the thickness of 3.31 mm (0.13 in).
If any of the valve clearances are out of specification, select new tappets using this formula: tappet thickness = measured clearance + the base tappet thickness - most desirable thickness.
Select the tappets and mark the installation location.
If required, install the new selected valve tappets in the marked locations. For additional information, refer to Valve Tappets in this section.