thumb test with starter to find any cyls puffing funny.
pull push rod cover. look for bent or thrown off lifter pushrods.
lastly. if you find a hung open valve. remove valve train and douse it with atf and acetone. use a deadblow hammer and work it back down then roll it back up with starter.. keep doing this.
might save you a head job.
I had valves stuck so bad I had to hammer them out that way.
good luck / post back