I never used the XE250 but I did run the XE 256/268 on my BBC.... Idled smooth under the hood but still had a rupity out the exh..... Alot of people like this XE series of cams and many dont like them...I'm one of the later... After 3 years I removed it and put a different cam in......These XE do tend to have a fair amount of valve train noise.... often times sounding like solid lifter cams.... in fact my solid cam and my old XE hyd make about the same amount of tappet noise.... Personally I dont mind a solid cam makeing tappet noise but a hyd shouldnt.Many of the XE cams use an XE intake lobe and a HE ex lobe..but the XE250 uses a faster exh lobe so this " might " tend to be noisy....... These do tend to be harder on parts than a more conventional hyd cam.... if you are ok with that then go ahead.... if your not then maybe something a bit less " extreme " might be better.
1969 El Camino
1969 LS-1 engine is a 427/335HP BBC
passenger car mill..( mine is slightly modified ).