da Rock

Except, I think that in reality, the negative pressure in the ventury (even at idle speeds) is greater than the pressures aerosman recorded. So even if the tank was pressuring the pressure line into that pumped up tank, that pumped up tank would be pushing fuel into the pickup line and the ventury would be pulling on that line as well. Which ought to/might possibly/maybe/could almost instantly kill any flow back toward the muffler. And it seems that the tank would have to be pumped to fairly high pressure for that pressure to overcome the pressure the muffler SHOULD be pusing into the line, even at idle, and the negative pressure from the delivery line. And the WOT pressure aerosman recorded isn't really much pressure. But who knows what the theory is that actually applies.

Because.... theory suggests that if there was residual pressure in the tank sufficient to force fuel back up the line to a muffler that's pushing back (no matter how little it's pushing back) then that same pressure ought to be pushing fuel at the carb when the carb doesn't want much at all, and one would think that would cause obvious engine idle problems.

I'm looking forward to aerosman's next posts.

BTW, aerosman, how far from the pickup point is the muffler pressure outlet? Normal uniflow theory suggests the muffler outlet hole be something like 1/2" from the intake pickup hole.