In my short time here at the bolt i've seen At least 3 threads about people discovering the tube pinched AND the broken piece in the engine somewhere. I'm starting to put together a theory on this one, let me know if I'm crazy.
People believe that pinching the return tube off in both the 235 and 216 increases the pressure to the rocker shaft and thus oils it better. The easiest, and laziest, way to do this is to take a pair of needle nose pliers to the tube and crimp it flat. They rarely cut it off since that could create metal shavings that could get into the engine. The pinched off but still hanging-on tube has a flat part and flat sections (think engineering section, like a beam) are weak in bending. Also, the pliers put a bunch of nicks into the steel which are actually stress risers. So now the owner goes and does tens of thousands of miles in his vehicle and the now relatively floppy tube with stress risers vibrates until the metal fatigues and the part falls off, hopefully not doing any damage in the process.
I found the end of my tube in my 235 at the back of the head up against the valve spring with valve spring marks worn into it.
That's my theory, even though it didn't answer your question.
Anyway, it should run fine with the tube pinched off.
