[Rich Biebel]

I CC'ed many heads in my engine shop days. I had no formula but obviously the bigger the head diameter of the valve the more you will change the CC's by moving the valve up or down in the chamber. It took a considerable amount of grinding of a 1.94 valve to change the CC's much. It was a slow process of grind and recheck. It was common to make heads 1.0 CC over the minimum. I did them down to .5 if requested. That was back in the days of using a hand ginder to do seats. The seat heights would not have been all the same unless it was a real virgin pair of heads and installing seats was not the norm either. Todays Serdi type machines would make the equalized seat heights easy to do.....If your heads were 3 CCs over......you can mill them .010" and should still be about 1 cc over......the factor for milling those heads is between .005" and .006" per/CC I don't recall the exact figure. We had a file for all the common heads.