I would try an induction heater on the manifold and flare nut wrenches. I would probably heat it, soak it, heat it, soak it, then heat it and try to unthread them. I have gotten things apart with my induction heater I thought would never come apart!!

That seems like the best approach, but they are a little pricey. I saw that you used one on the intake manifold tube fitting and was intrigued. I've used a torch and ice cubes in the past, but it was not very effective on the manifold because of its size I think.

9 hours ago, Patcon said:

I would try an induction heater on the manifold and flare nut wrenches. I would probably heat it, soak it, heat it, soak it, then heat it and try to unthread them. I have gotten things apart with my induction heater I thought would never come apart!!

I did something similar on mine a few months ago but with a blow torch:

Heat till red hot around the manifold, cool the threads a little with pb blaster, little pressure on the threads with wrench. Repeat for about two hours until all were loose. It caught fire several times, but I did this outside surrounded by snow.

@motorman7 I think I paid about $150 for mine on Amazon