3D drawing SBC Valve Angle Verification

[383ssmonty]

I figure this is as good a place as any to ask about the valve angle on a SBC 23 degree head. I keep measuring 22.5 degrees instead of the 23 degrees I expected from the common description. I'm trying to draw one using SolidWorks that I may be able to use as resume bling of sorts, and I'm trying to do the best I can to get everything dimensioned correctly with the rather crude tools at my disposal. I would like to create an entire engine assembly in 3D eventually just because, and I may be able to help others questions with pictures (worth a thousand words).
I'm about to start drawing the chamber and its going to be a lot of effort that I'd just assume get right the first time. I'm going to do some runner casting so that I can get dimensions in the future, and will be returning here for suggestions I'm sure, but for now I'd just need to verify the valve angle with someone that's done some machining on a mill or whatever to find out if 23 is the correct design angle or an abbreviation for 22.5 (1/2 of 45 for easier machining reference)?
Thanks for any and all replies,
ssmonty

[Kevin Johnson]

23 degrees

http://www.chevelles.com/forums/13-perf ... s-etc.html

You may very well be measuring 22.5 degrees with an example of the head.