Well chaps, I have left this for some time just to see what calculations or guesses were put forwards. No responses so far so perhaps no one really cares. Let me go through the calculation and then some of you can check to see if my two remaining neurones are still working.
Start with a figure of one G is 32 feet/sec/sec (that is per second squared). Having measured many Vincent cams up over the years a typical figure for the maximum positive acceleration, which occurs at the start and end of the lift, is 0.0005 inches/camshaft degree/camshaft degree. Incidentally, the maximum negative acceleration which is when the valve spring is controlling the valve motion should be about -0.0002 inches/camshaft degree/camshaft degree but because of the nature of the flat based lever cam follower on Vins this figure is exceeded on all Vincent cams. Now at 6,000 engine rpm the cam is going at 3,000rpm so the question is how much time is taken for the cam to turn one degree. 3,000 rpm equals 50 revs/second, divided by 360 to give the time for one degree of camshaft rotation gives 1/50X360 of one second. However, note that we are here into degree/second square or per seconds squared so the above figure has to be multiplied by itself for us to work out the 'G's. So we now have a figure of 1/(50x360x50x360) which for those who care gives a figure of 1/32,4000,000. Multiply the value of 0.0005 inches given above for the maximum positive acceleration and we get 13,5000 ft/sec/sec which is about 422 G !! Go on, admit it, you knew that anyway didn't you? Calculating the reciprocating mass of a valve train is somewhat tricky as one has the valve, collar and spring cap and push rod reciprocating, the cam follower and rocker oscillating but a figure of about one pound weight will do for this purpose. Therefore at 6,000 engine rpm one has the cam and follower etc thinking that it is moving about 422 pounds weight. Note that there is a 'squared' in this so that at 1,000 rpm one has to divide this figure by 36 to give about 12 pounds weight.
Going back to the negative acceleration controlled by the valve spring and using a figure of -0.0002 inches/camshaft degree/camshaft degree we get a 'G' figure of about 169 pounds weight. Now you know why your valve springs are as strong as they are.
So now going back to the advice to rev the engine upon start up. Turn the engine over as slowly as you want and there are certain forces on everything. Rev the engine and you still have all those forces plus the inertial loading due to the 'G' forces caused by the acceleration of all the valve train components. Do you still think that it is a good idea to rev an engine from cold?
Now with regards to starting a new engine and anti scuff compounds. Everything above pertains to used engines being started after sitting for a day or a year or whatever. It is true that there are a variety of products made to aid the start up on new engines without too much wear on the highly stresses components like cams and follower. Some of these are intended to be 'stuck' to the components by baking or whatever. Putting on a grease ,unless it can give a molecular bond, is unlikely to be adequate. Using the above figure of about 400 pounds weight for the inertial equivalent of the valve gear consider that the whole of this movement it being produced by the movement of the cam follower around the cam. Let us take an area of half and inch wide by one thou thick as the pressure point between the cam and follower. That is a total area of 0.0005 square inch. This gives a resultant pressure of 2,000 times 400 i.e. 800,000 pounds weight/square inch. Eye watering isn't it.
Now let me know what I have done wrong.