You can lose compression, but not if they are the same chamber volume.
The 302 are 64cc. 360 heads range 70-72cc,X heads are around 69cc.
302 head ootb flows less than an open chamber 318 head and 273 closed chamber heads. They are just a chamber..and even that shrouds the ever living **** out of the valves. They need a ton of work.