quote:Why would that break?
My best guess so far...
As long as I've owned the car the top of the air cleaner showed witness marks of contact with the leading edge of the rear decklid. It's been like that for years. However, when I rebuilt my engine I swapped out the Edelbrock Performer intake for a Weiand Xcelerator 2V single plane intake manifold which I had the carb pad milled flat to minimize interference issues with the air cleaner and the rear decklid.
My best guess so far is that the air cleaner may sit a tiny bit higher with the changed intake and the decklid is making contact with it, applying a constant load rather than the occasional vibration scrape. I suspect a constant load or stress on the air cleaner stud combined with 3500+ miles of engine vibration may have work hardened the stud and caused a stress failure which occurred right atop the locknut I used to secure it to the carb to make sure it couldn't ever back out.
Tear down starts tonight. I'll share what I find.