2&1/4" is 35.5 degrees. I'm assuming you are wanting something other than run it up till it wont advance anymore & taking a reading with a dialback or timing tape. If remarking the dampener .0632683" along/around the circumference is 1 deg. I use a 0-1 and 1-2" mikes to measure strips of paper to set my initial from the vacuum gauge method and after shortenening the slot the total I want, 35-SB 36-38-BB 31-magnum with good quench