I took the heads off so I could get some broken exhaust manifold studs out and retap (actually I was advised to use a Heli-Coil instead so doing that) one of the other stud holes.
The image of the piston heads is after five hours of scowering, a lot engine degreaser, carb cleaner, wd-40, and even some scraping. Yes there are some teensy weensy abrasions on the piston heads now but before it was coated with a rough surface of carbon so I'm pretty sure it's better.
To be honest I'm not even sure why I did it other than they were really filthy and I saw a YouTube video where a guy did it so there wouldn't be any hot spots on the pistons (not wifi hotspots obviously but like with temperature). Did I even need to do any cleaning (sorry, no before picture but they were coated in black and it was even a bit lumpy on some of the edges)? Is what I've done good enough or does it have to be perfect?
I haven't touched the bottom of the valves yet. I don't want to disassemble the heads so I'm really hoping just cleaning up their bottoms will be good enough. What do you think?