Here's a video I found recently about additives and if you look at his other videos they are very informative and he does testing to come to his conclusions not just repeating what he has heard.
While the videos are geared more to modern engines I still think it applies to all ICEs...
Check the distributor cam to see if all the lobes are consistent.
Here's a video that uses a dial gauge to check the cam and point gap accurately.
https://www.youtube.com/watch?v=y2R-ljyf9eg
I had a sticking throttle and it ended up being the tillotson carb, I switched it to a zenith and it stopped. That tillotson was on a different car before that and never had any problem so I'm not sure why it would do it on that particular car. The throttle shaft would start sticking and if I...
I thought about grinding out the cracks a little and using some JB but I'm worried about the crack near the #2 spark plug especially with the higher compression.
So after leaving the head in a rust911 solution for a day and cleaning off I think I know why it was sitting on the shelf. It has cracks across the top of the head and I don't trust it enough to try it out.