As Mr. Cox alluded to, it's "some other" problem...

ALL of our engines would die the second we pointed them straight up if the tank height was truely the issue people seem to make out it is around here.

Tank height primarily affects the plane while it is sitting on the ground, as fuel can siphon out of the carb, or back into the tank.

Once the engine is started, muffler pressure makes it a relatively small issue.


I've had what you describe occur, because I made my fuel tubing too long, within the tank.

The clunk would flip "up" during a roll or some other manouver and stick "high" in the tank while the plane was flying level.

Shortening the line fixed the problem.


Also when your tank is down to about 1/3, as in your case, you have to remember that during downlines air can get into the clunk & lines.

There is a myth about the "fuel sticking in the back of the tank" which is totally untrue...

At 1/3 tank, even a slight 20 degree dive can uncover the clunk. If this happens for more than a second or two, the resulting bubble will cause the engine to cut off.

You COULD attempt to richen the low end up to help keep the engine running through the fuel starvation... this often helps... but it will degrade idle a bit.