Originally Posted by
BMatthews
If it wasn't clear from Richard's post then let me stress the idea that fuel draw is a problem for any model engine that does not use some form of fuel pump. So with regular glow model engines moving the tank back more than about an inch from the rear of the firewall is almost certainly going to introduce fuel draw issues and lousy engine runs.
On my Venus II with the tank just behind the firewall, I notice the engine leaning out on long uplines once I've burned off half the tank of fuel. I need to set it at least 400 rpm rich on the ground to prevent this. And yes, I use muffler pressure and the line and fitting are open.