Muscle LLC advises to use a 12 point 20MM socket for the nut, which interestingly made me aware that metric sets for some unknown reason all go from 19 to 21. Why do they skip 20? Regardless, I picked up a 12 point quality 20mm socket and it didn't work so good, it started rounding almost immediately. I used a 12" crescent wrench and I got it. One part Muscle LLC doesn't advise in their autopsy, is that after the factory manufactures these, there's a machined rectangular punch at the top on the brass near the rim where the nut goes in, that I suspect acts as a "lock", anti nut back-off preventer and the inner nut shank area is machined like dental bridging to prevent back off. The brass is soft enough to remove the nut and just a slight tap after the rebuild to re-lock it prevented any leakage whatsoever from the threaded area, mimicking what Kelsey Hayes did seemed the only logic, the inner threaded area behind the punched area was deformed slightly which triggered the locking theory. Perhaps that was a mistake on my part, not sure. The leakage was at the pin and, it very well may be bent. The pin did have a little play upon rebuild after install and I did suspect it may of been bent which may of contributed to it's catastrophic failure, I did recently change the spark plugs and may have tapped it causing its demise? But it only leaked when pressure was applied unlike the 2 previous Inline pieces which just leaked outright. Just the same there is a happy ending, I just received my 3rd Inline block hours ago, installed it, and it's dry. In this case, the third one from them was a charm. Thanks all regarding.