Lifter failure
I have only broken in one FT cam, that was last summer.
I did the lube, comp breakin oil, and then made every mistake possible and it survived.
Started and stopped the engine no less than 8 times due to various reasons that I had no choice on.
Then finally the 20 mins at 2-3K.
Made me a believer in the cam saver lifters, or I just got lucky.
I have a 1970 440 with steel crank that I will be building this winter, and i will for sure be going roller.