i just like to know if these are the same as a 2171 Jonsered.or are they diffrent in mm of the bore? i know the 2171 jonsered is a 50mm bore and i don't know what the 2150 jonsered is.i was thinking about doning some porting and try my hand in it to see how good i am.i can get this jonsered 2150 for 175.00 and i was thinking about getting it to try my hand at some port work.