328 timing side camshaft sealing

I´m going to replace the camshaft sealings on my 328. Is it necessary to remove the camshafts? Do you recommend to install the o-ring dry?

best regards

Michael:
Conceiveably the cam seals could possibly be replaced with the cams in, however, it will be very difficult to insure the seals go in with out damage.
It would be impossible to replace the O-rings with the cams in.
After everything else is out, it is fairly easy to R&R the cams--not sure why you would want to do the seals without R&Ring the cams?
Mark

Mark:
Thank you for your answer. Now that i have removed the cam covers its quite clear that their is no way to replace the O-rings except removing the cams pullers etc.
regards Michael