The sheetmetal that covers the rockers is held in place by the valveguides. I dug up a piece of pipe and a few washers from the scrap iron and fabricated a little puller to remove the valveguides without damaging them. Worked like a charm!

Now that the head was stripped as far as possible I could start measuring. I used a granite surface plate, a digital height gage, various digital calipers and a digital angle tool.For me the CAD modelling itself is relatively easy, the challenge is in getting all the measurements correct!