o type head from morris 1800

Has any one had any experience in the performance after fitting the o series head on an mgb
I have a 1971 mk11 with a sports cam and have been told by dealers that if done correctly it would greatly increase my performance Also someone has mentioned that the x series is better
regards
ptobin

I am led to believe the O denotes 'O'versize valves.
I have had one of these heads fitted to my MGB in the past and dont feel you would notice a difference unless you had it on a dyno. Other mods (Cam, etc) may help the head show its true colours though.
Have fun.