Arch,

If you've managed with muffler pressure, that's great; installing pressure taps in crankcases is not something I'd choose to do if it wasn't necessary. But... That simply may not be enough in some instances where positive pressure may be needed. Free flowing exhaust systems may not provide enough pressure to the tank to push the fuel to the regulator depending on a variety of factors. The Walbro system doesn't pressurize the tank, it pressurizes the fuel (through the use of a diaphragm pump driven by crankcase pressure pulses) which is then regulated by the regulator (hmm, that sounds like an echo!). It's (the Walbro, that is) like using the IB regulator in conjunction with a Perry pump; the fuel is still pressurized- just not the tank.

Maybe what it boils down to is this: If I'm going to the trouble of hooking up a regulator style system- be it Cline or IB- I'll take the extra step and tap the crankcase to ensure I have an effective and consistent fuel supply- which is really what a pumped system is all about. That's just me, though, a glutton for punishment, I guess.

Good discussion, we need more of this!