Originally Posted by Jrsgrabber50
How many rpms is the stock rated for before blowing up
Ford doesn't usually say it that way. They specify the redline as the highest RPMs the engine should routinely see to allow for two things: a reasonable certainty that it won't lunch itself due to a high-rpm problem like valve float, and a reasonable life span for components.
So, if Ford set the redline at 7000 RPM, it is possible that the engine might wind up to 9000 before valve float, lubrication issues, etc. cause actual problems. It is also possible that anytime you go over 7100 you have a 5% chance of a catastrophic failure! We simply don't know because Ford doesn't publish the results of all the dyno testing and simulations they did to arrive at the 7000 RPM redline figure.
We do know that Ford (as most manufacturers) leaves a bit of a safety margin, so it is likely that the engine can see 7200-7300 on a regular basis without much danger, but that is just a guess.
In conclusion: On a stock motor, I'd leave the stock redline in place. If I added FI, I'd go with the recommendations of the FI manufacturer.
P.S. If anyone has any Ford engineering insight and test results I'm sure we'd all like to see them.