Chapt. 1, Expanded Content, No Load RPM Limit?

I've been taking some classes at the local technical college and I've been fed so much wrong information in the textbooks that I'm having another run at PD's book.  It's refreshing.  

I was originally taught that running an engine with no load at anything above idle was just asking for a thrown rod.  Clearly that is not the case (well, maybe if the rod already has one foot in the grave).  Now I assume that the 3,000 RPM fuel trim check is done just long enough to get the numbers.  So, on an engine with no load (park/neutral), what combination of RPM/time is getting to the danger zone?

I'm not just asking for the fuel trim check.  I'm curious how hard you can push an engine with no load, for whatever reason?  I seem to remember that Paul had a student over-rev an engine in the shop and throw a rod.  Does anyone know the numbers on that incident?

I remember Paul talking about that, I am going to go out on a limb and say that was an isolated incident.
I'm afraid you've been misinformed, don't be afraid to rev an engine with no load.
Before I started using a vac fill tool to fill coolant systems, I would hold and engine at 3,000 rpm until my hearts content to bleed air out of coolant systems.
The only time I'm ever really cautious is when power breaking an automatic. In gear, foot on the brake, revving the engine for extended periods of time can overheat the transmission.
If one in a million throws a rod because you free revved to 3000 rpm, then the engine was sick anyway.
How far can you push one? Well, I would like to challenge you to blow one up simply revving in park. Aside from my 1991 Mustang, nearly every fuel injected engine will go into fuel cut to prevent over rev. (The Mustang WILL let you throw a rod, but it's not going to happen at 3000 rpm, it might float a valve at 7,000 where it has no business operating...)
I can remember in my early junkyard days dropping a brick on the gas pedal of a Dodge Stratus and growing quite bored waiting for it to self destruct. (Which didn't happen)
I had a boss hold a Focus at 4,000 for a VERY uncomfortably long period of time to eliminate a top end tick. (Which actually worked!)
As long as the oil pressure is good, it's not overheating and not knocking, rev away.

I don't remember a video with Paul mentioning the thrown rod? But that doesn't mean anything. 

I'm curious how hard you can push an engine with no load, for whatever reason?

Pretty much as hard as you like, in my experience. I can't recall anyone I've ever worked with causing damage to an engine while revving it with no load. 

Part of my normal cooling system repair follow-up process is to hold the engine speed at 2,000-3,000 and force the cooling fans to cycle on and off at least once. Stress test for the cooling system as a whole. Hate to be that 'I've never had an issue' guy, but, well, I've never had an issue.

BG MOA services are similar. The instructions have you hold the engine speed off idle for 15 minutes during the service.

What's the danger zone? Don't think there is one. Like Noah said, you'll probably get bored of listening to the engine before anything fails.

I can remember in my early junkyard days dropping a brick on the gas pedal of a Dodge Stratus and growing quite bored waiting for it to self destruct. (Which didn't happen)

I've had older techs tell stories of the Cash For Clunkers days. They were always blown away with how long it took for the engines to pop with the sodium silicate additive and free-revving them to the moon.

I appreciate the replies. I don't even remember where I picked that up. It was certainly over 50 years ago. Hell, I remember when it was accepted as fact that sitting a flooded lead acid battery on concrete would ruin it.