I have an old O.S. .40 FP engine in my dad's old falcon 56 mkII airplane, and I keep getting air bubbles in the line. i'm going to be flying soon, and at first I thought it would be all right, but now when I rev up the engine, so much air goes in that it completely stops!!! HELP!!!! all the lines are tight, so I don't know where the air is coming from

Have you checked the klunk in the fuel tank? Make sure it is on the line and isn't hung upwhere it will suck air

Also, if the tank is not padded properly, vibrations will cause the fuel to foam. Even if the clunk is at the bottom, it will suck up foam instead of fuel.

The Klunk is at the bottom, and the tank is completely surrounded by styrofoam, my dad had custom foam done for the tank, and the radios

one more question, which needle is the low end adjustment, There is the high end that is the easiest one to access, and then there are two more smaller ones on the carb that are harder to get to. which one is the low end, and then which way leans/richens?

Don't use styrofoam. Use some padding foam instead. Styro is too rigid and won't absorb the vibrations at all.

If changing to regular foam dosen't work, try a sintered bronze pickup.

Andy

a651: thnx, switching to padding foam fixed it

Also look for a small hole in the carburetor fuel line INSIDE THE TANK. It may have gotten pinched and split during assembly. That'll give air bubbles for sure.

No styrofoam. Use foam rubber. Even a wadded up old paper towel works beter than styrofoam!