Okay, I understand better now which way you are tilting the engine. But it doesn't really change my thinking. I find it hard to believe that a model will sit on the ground perfectly parallel, with the engine exactly straight and perpendicular to the earth. Two washers worth of tilt is only going to be about 2 degrees, which is not enough to have that type of effect. I have heard of tilting the engine 15-20 degrees off of vertical in an inverted position to keep the plug hot, but I really don't think any less than that would make any difference. There is something else going on here, and we can speculate all day about it. I'm still thinking it is something external of the engine, and not pooling of fuel in the plug.