Hallo Torsten, und willkomen . . .
Personally I think that the porting ideas from the now 70 year old speed manuals have not stood the test of time and engineering knowledge.
The intake side of these heads is limited by the valve opening - not the port. So what is to be gained by increasing the size of the port? The answer is nothing. And in fact we give up velocity through the port when we "hog out" like the Fisher speed manual suggests.
On my 216 build I focused on removing the ridges from the floor of the port and smoothing the back wall:
Frankly if I had to do again - I would raise the floor to the level of these ridges. Not sure what a suitable fill material would be.
Moreover, the biggest gains from porting on these heads comes from focusing on the exhaust port - with particular attention to matching the port size with the gasket - followed by a thorough smoothing.
Looking forward to hearing more about your build.
viel gruess,
stock49
