I realize there is no spark to cut, and limit RPM, but do these engines have anything to keep the user from spinning it past a certain point? I have hit redline a couple of times.

 

Yes, all diesels are governed, mechanically or electronically depending on the injection pump. You can hold the pedal to the floor in neutral and the engine will only rev to whatever RPM the governor is set to. If you're going to try this, don't just mash it, roll into it slowly - the engine can rev quicker than the governor will react, this is known as flare. You can over rev the engine by downshifting a manual trans to too low a gear for your road speed, this is about the only way to bbreak the crank on a stock motor. As far as how fast you can spin it without damage, the 12 valve is OK until 3k, at which point you need stiffer valve springs. With the stiff springs or a 24 valve, they will stand 3800 - 4000 RPM without blowing up.

 

On the Excursion I can rev to 3800 with 10psi in PARK. Without the chip I can only rev to 3300 with only 4psi in PARK.

 

Ok thanks for the info, so at what RPM are they governed? I went to around 3600 the other day, didnt seem to be cutting out or anything, although it did seem to be de-feuling as the power dropped off rapidly.

 

Yeah, since it just decreases the fuel flow the engine will be smooth at the top RPM, it just won't go any faster. I'm not sure of the max governed RPM of the ISB in the Dodge, to find out just put in in nuetral and slowly push the gas pedal all the way to the floor. Don't stomp it, roll into it, and the revs will climb to max governed RPM and stay there. Won't hurt a thing and you'll learn what max RPM is on your truck.