These engines are run to over 10,000 rpm in Australia. The standard valve train is used as a baseline and I will make a simple and semi-accurate analysis to see if I want to do the same. The valve train stresses are proportional to the reciprocating mass. Heavier parts make more stress. The reciprocating valve train is considered to be the intake valve, 1/3 of the valve spring weight, the spring keeper, and the collets. The stock Triumph setup weighs 97 grams. The racing system, wit a 2mm larger intake valve, weighs 83 grams. [(97 - 83) / 97] x 100 = 14% less weight
The valve train forces are proportional to spring stiffness. Seating force with the Triumph spring is 45#. The spring force with the race springs and no shim is 52#. This is adequate for milder race cams. The spring force with race springs and the shim is 60#. The shim will be used, so this is a [(60 - 45) / 45] x 100 = 33% more spring force
The standard rev limit was 7,300 rpm. The rev limit I am using now is 9,000 rpm. The Aussies are using 10,000. This is 3,650, 4,500, and 5,000 cam rpm. The valve train stresses are proportional to the rpm squared. Squared, in millions of rpm, this is 13.3, 20.3, and 25.0 Using 4,500 rpm, the increase is [(20.3 - 13.3) / 13.3] x 100 = 53% more stress. With a 5,000 rpm rev limit, the increase is [(25.0 - 13.3) / 13.3] x 100 = 88% more stress.
Adding up the pluses and minuses for a 9,000 rpm rev limit, 33 - 14 + 53 = 72% more Doing the same for a 10,000 rpm rev limit, 33 - 14 + 88 = 107 percent more. This assumes the same cams for both situations. It does not consider the greater stresses from a more aggressive cam or the thinner oil film in a more highly tuned and hotter engine.
I am not sure which way I will go.
dli{(on the engi