Formula for CC displacement

Rich Biebel · 01-18-2009, 08:22 PM

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.

Chad E532 · 01-18-2009, 09:14 PM

Would it work to take the area of the valve face (in square centimeters) and then multiply it by the height change of the valve in cm to get a close approximation of the cc change in the chamber?
You would have to assume that the valve face is flat and that it basically creates a 3D cylinder of volume as you move the seat.

01-18-2009, 08:22 PM	#1
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,320 Likes: 25 Liked 557 Times in 217 Posts	Re: Formula for CC displacement 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. __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 01-18-2009 at 09:08 PM.

01-18-2009, 09:14 PM	#2
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 7 Liked 54 Times in 7 Posts	Re: Formula for CC displacement Would it work to take the area of the valve face (in square centimeters) and then multiply it by the height change of the valve in cm to get a close approximation of the cc change in the chamber? You would have to assume that the valve face is flat and that it basically creates a 3D cylinder of volume as you move the seat.