I recently purchased an older RV-3 with header tanks. There was some trouble with the vent, which appears to be non-standard. I was wondering if anyone could describe or take a picture of the vent system for the header tank.
They installed a pitot-like ram air vent. I think the issue is that it can't actually drain properly with full tanks and high climb angles, so if the tank is full, it overboard into that tube and causes a partial vacuum. There are no pumps and the vent tube is at the same height as (maybe even below) the carb and causes a back-siphon effect.
The solution the previous owner did was to put a hole in the cap, which is prone to water fouling [fowling], I wanted to know how the header tank should be vented to work properly without a fuel pump.