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Interesting......

My thought on the "valve float" is that the only time that exhaust port pressure would be higher than cylinder pressure, AND the piston is close enough to TDC that the valve could hit it would be at the very beginning of Intake valve opening. At the top of the exhaust stroke, cyl pressure is going to be higher than port pressure (the flapper is closed, so the exhaust stroke is just another 'compression' stroke) so no possibility of the Exhaust valve being 'blown open' until the cyl pressure is lower than the port pressure behind it. I don't know how much overlap, or how far BTDC Intake opening begins in a Powerstroke cam, but once the piston is moving downwards, the piston can't really damage the exhaust valve if it does hit it. Another consideration with valve float is that pushrods, rockers, lifters and the cam can be damaged by the valvetrain banging back together.

Has anyone actually seen damage in a Powerstroke that was caused by exhaust brake valve float, or is this pretty much hypothetical?


The transmission concerns on the other hand do make sense. I have a Pacific Brake in my 99, and the last couple of times I attempted to use it, it didn't slow the truck down. Even in "overdrive off", there is no engine braking. I suspect something may be developing in the trans. For now, I just don't use the Pac Brake. Not to mention the flapper got stuck closed. I wondered WTF was wrong with the truck. It couldn't get out of its own way. I don't tow heave enough chit to need an exhaust brake. Eventually I'll take it off, but for now its unplugged, and I don't use it.
 
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