The Stovebolt Site Forums The Shop Area Driveline Is it worth changing out diff gears?

How many illegal mind-altering substances are you on?!? You aren't even close to valve float. I don't have a 235, but I couldn't imagine valve float happening at less than something like 4,000RPM (I'd guess higher). You have to be running less than 2,500RPM! There are lots of reports of guys with full-pressure 235's running well beyond 3,000RPM on the highway with zero trouble. What about a grain truck? Forget about driving speed; how are you going to pull the wide gear changes of an SM420 in a heavy truck if your valves float and your engine quits making power at 2,500RPM?

I have 4.10's and a 32" tire on my current truck, and my slightly later 250 six would purr like a kitten running 80MPH if I wanted to pay for the fuel! The later sixes are a little better/stronger, but not by that much. I normally drive 55-65MPH; I could exceed 55MPH in third gear before the valves float!

BTW, valve float under load isn't "a quick way to burn valves", it is/would be a quick way to drop one into whatever cylinder has the lamest valve spring and blow the engine up.