I put in a call to Crane Cams to ask about the life expectancy of their aluminum rockers after Ford Racing told me to call them. They manufacture the Ford M-6564-A351 rockers. I told the guy at Crane that I called Ford about the life expectancy of their rockers and before I could say that the Ford guy didn't have an answer, the guy at Crane sarcastically said, "They said 20 thousand miles, right?" That Summit catalog generated a lot of calls for them and he seemed annoyed. He told me that they can and should last a long time in a daily driven car if they are properly installed and the oil is kept clean, but that if I was worried I should check them.
The Ford Racing guy wouldn't put a life expectancy number on them, but he did say that in the 8 years he's been working at Ford Racing that he's never seen one fail.
I just thought I would let you guys know what the manufacturer said. I still plan to check them when I pull my engine next spring.
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351W 89 Mustang GT Convertible