Cam tight in F4R head

Chaps,

Has any one come across a cam that's quite tight to spin by hand? I have a clio head and the exhaust cam is stiff to turn even with no cover on. I ve tried 3 cams even the original one and all are the same. :scratch: the inlet moves freely with little force. With the cover on, torqued up and no valves etc, I can just about turn it with the pulley. Also no tight spots, its the same through 360 deg. What you reckon?

if the head has overheated or warped at some point this will happen to any OHC head :(.........the camshaft is true but the head is no longer true!

I bought the head second hand with bent valves.:crap: really struggled to get one so took a gamble. Really peed off! Can it be rectified at a machine shop that line bores?