I have a evolution .46 on my Spad. And whenever I do a steep climb or I do a loop it dies at the very top. I was going full throttle and then I pulled a loop at the very top my engine was very very close to cutting out. Does anybody have any idea on what this could be? It still has the same glow plug in it. This is the first plane it ever did any manuvers in.

Blitzz

There are a lot of things that could cause it. The first thing I would check is the high speed mixture. It could be starving for fuel at those attitudes and may need a richer setting. One way to check is tune the engine normally on the ground and then hold the plane straight up or even on its back to see if it tries to shut off. If so, it may simply be that the position of the tank requires a richer setting to do those maneuvers.

Anybody have other ideas?

The clunk in the tank is too long and hitting the back of the tank and not following the fuel in the loop and stopping flow when vertical. or what was already suggested you are too lean on the high end.

I also think your mixture is too lean,tank height,clunk hitting the back of the tank will both cause a lean condition,as suggested before try adjusting the needle on the ground and then holding the plane nose up.and you may also want to try this with different fuel levels in the tank(example) full tank,1/2 tank,and then 1/4 tank if you get it working good with a full tank but then are having problems at 1/4 tank check your tank height.hope this helps.
Steve
AMA#511248

I think I found the problem. I took out my fuel tank adn the clunk was curled up at the top of the tank so when it went vertical the engine wasnt getting any fuel. I will also try richining it a tad.

Blitzz

Great! That's a common occurence. Usually after a hard nose in landing or abrupt stop. Afterward, it's good to remember to give the plane a good jerk toward the tail and back to be sure the clunk is free.

Add a piece of stiff tubing (Plastic, brass, or whatever) to the clunk line. This will allow it ti swing to all areas of the rear of the tank but it won't let it swing forward.

Ok the engine is running perfect now but I cannot get my muffler tight. Once it is warmed up it will spin around and around. The bolt and the muffler are stripped so do you think i should drill out the muffler and just put a bolt on it instead of it being threaded or try and put a few drops of j-b weld on it?