Does anyone have any idea of the valve seat pressure with a set of standard springs, Newman doubles and Iskys.

I am under the impression that Isky Valve springs can be fitted to a standard head ( un-modified spring seat) without coilbinding until 10.5mm of lift

 

upski.

 

I have the figures somewhere but I remember that they wont coilbind. However if you are running dual valve springs the pressure would be to high and you run the risk of causing excessive wear if running them without modification to the head.