That is a trade secret Coleighf . . .
Cylinderhead and barrels had returned from the blasters so now time to attack the engine starting with the cut stud. I took to 2 engineering firms who both failed to remove the stud. I was looking at spark erosion when my son-in-law offered to do it. He assured me he had the skills and even came to my house with hand tools and demonstrated his expertise. 2 1/2 hours later . . .
New stud fitted and spare barrels and head were fitted ready for me to try my soda blasting