Well Bob got my interest with this little quip:
https://www.dieseltruckresource.com/...d.php?t=105408

So I tried to see how far mine would rev with the new smarty update. Before I'd made it to 3500 on a few occasions, but this time I stayed on it all the way to what looks like 3750.

Do I need to run the truck past redline? No. Is it good for the motor? No. Is mine built to take those rpms? No. I was just curious and thought I'd share

I too wonder what those right mods are

 

I think stiffer valve springs would be important when running higher RPM's

Randy

 

That and retainers. Max power is made below 3200 so this was mainly a curiousity thread.

 

Even though peak power is at 1800 RPM, an extra 2000 RPM on top of that would allow you to run really tall gears without running out of legs at the top of the quarter mile.

The engines sound good at 4000 RPM, too.

 

a properly built 12v puller sounds like sweet music in the 6k rpm range

i took mine to 3500 once when i broke my shifter off and had to drive home all the way in 3rd gear, i noticed the engine smoothed out and got quieter and looked down to see it was at 3600...i promptly let off and continued my drive home at 30mph

 

I'd say the mods would be the ones sold by Don M... new valve springs and a helix cam... I've ran my RPM's pretty high(3500+) and you can definitely tell it's out of fuel as I have no fueling box.