Originally Posted by
Jeff Higgins
Yup, I can definitely see that - we would be adding the weight back to the rocker arm tip that we were able to lose with the elimination of the adjustment screw and lock nut. Maybe even more weight, with the axle, roller, and change in profile on the rocker arm to accommodate.
I do suspect that the available valve spring materials of the time were a crucial limiting factor. We have seen tremendous advances in that arena in the intervening time. 8,000 rpm back in the 906's day was really something for even a small bore motor such as that, where today we see big American pushrod V-8's turning over 9,500 rpm for 500 miles in the unrestricted NASCAR short track stuff. The NHRA imposed a 10,500 rpm limit on their 500 cubic inch Pro Stock motors - the well funded teams were hitting 12,000 rpm. With a 500 inch pushrod V-8... with 2.25"+ diameter intake valves... so, yeah, the material sciences have met these demands.
I have to think that the demand just isn't there for our motors. Everyone racing them is restricted to in-period equipment, so there is no real reason (or ability) to take advantage of these modern day developments. We do, of course, see all of this applied to modern racing Porsches, where it rightly belongs. Just not in our wonderful old air-cooled world.