Oh wow, it's actually going in smoothly.
It's a miracle! I can't thank everyone on this forum enough. I was really frustrated yesterday but the vertical hacksaw holes/chisel with a screwdriver technique really does work.
If anyone else comes across this post and is also confused/annoyed like I was, I think the reason I was so confused is because everyone was saying to "chisel" and my entire life, chisels have been precision woodworking tools that are quite large and sharp. What everyone meant was, "use a little punch or old screwdriver *like a chisel*" because my chisels were just violently piercing through the thread and the engine manifold and anything else in their way like butter so I was confused how this wouldn't just destroy the threads. You basically need a tiny, dull chisel. I used a long, old screwdriver. And you're not making a cut with the chisel, you're making a forceful downward force that breaks the old coupling at the weakest points, which you made with the hacksaw. Then you're pulling it off, towards the center of the hole, not up, with the pliers.
