RE: Norvel Engine FAQ
It's just that sometimes another set of eyes can spot something that might get missed. Pictures always convey a great deal more info, anyway.
I do know that car fuel typically does not have the proper oil content needed for aircraft engines, i.e., not enough. It has, in part, to do with the differences between car and aircraft throttle usage and the dissimilar demands that this puts on the engines during use.
"when I try and turn my needle backwards (twisting it right if you are looking at the side with the needle, I cant close it all the way."
Clockwise closes (leans) the neddle valve setting, also referred to as turning the needle "in"; counter-clockwise, or, "out", opens (richens) the needle valve setting. When you feel resistance, the needle is all the way closed (unless there's foreign matter blocking it). Don't force it past this point. This is a rule that applies to any and all engines with needle valves. You'll have to wait for someone with specific experience with Norvels to answer your question about the exposed threads (though this is often normal on other engines, as it is with Coxes, for example).
Were you using the car fuel because it has a higher nitro content that your aircraft fuel?