I wouldn't recommend it. The only thing that is happening at those RPM is the breaking of rods, rockers, and valves kissing pistons............. There is nothing happening horsepower wise. All you are going to gain is a nice pile of broken IDI parts, not power!
What Heath said...frankly, this is one of the things I've always been afraid of. dyoung's been experimenting...but, just because he's done it doesn't mean that it's safe or a good idea, ESPECIALLY on a stock engine. At the VERY least, you need stiffer valve springs, to overcome the tendency for valves to float and/or lose their keepers and get swallowed
and you also have to be concerned with the rotating mass and how well that's going to hold up.
Just to clarify, what I've been afraid of in this instance is that someone would read dyoung's posts and assume that it's safe to over-rev one of these engines based solely on what he did. I would rather strongly recommend reading through all of his posts, paying attention to the issues that have come out of his experimentations, before going through with that. And, I've said it before, but please let me say it again...I firmly contend that the engineers at IH limited these engines to 3400 RPM for a reason. For that matter, they're limited to 2800 RPM in IH applications...so, they already brought the governed RPM's up on a Ford application. If you want to go beyond that, go for it, but keep in mind that a) you do so at your own risk and b) there are potentially significant dangers involved....to your engine primarily, but there's a potential safety concern if you experience an uncontained engine failure...
Just my $.02...
