On my 97 max 240K i have a damaged bucket and shim is gone. Engine makes loud ticking noise
since clearance is big now on that exhaust valve. Can i unbolt camshaft and move it enough to remove
old bucket(lifter) and install new one with new shim or do i have to remove timing cover ?

 

Id say that you do need to remove the cam before you can replace the bucket and shim..

So yes. You do need to remove the front cover.