im_a_rcav8r

I just got an old O.S. .25. It is from when they used an exhaust valve linked to the throttle. My question is this: Do I have to mount the fuel tank higher than the engine for fuel flow, or is there some other way. This engine does not have a muffler and does not appear to be built to take one. The exhaust valve would not operate it a muffler was put in place.

Flypaper 2

Should be able to take the ex. baffle off, get an aftermarket muffler for it. They use a metel strap screwclamp that goes around the cyl. Most have a pressure fitting on the muffler but would run fine without pressure. the carbs back then had a smaller venturi than used now so had good fuel draw.

J_R

The tank needs to be mounted in the normal location (fuel supply same height as carb intake). The tank has to be vented to the air. If inverted flight is being considered, it must have two vents. The first vent should be done in the typical manner, with the fuel line exiting the bottom of the aircraft. The second vent should be installed 180 degrees from the fist one, with the tubing then exiting the top of the aircraft.

The reason the vents need to be outside the aircraft is so that air will flow over them during flight and provide some small amount of pressure to the tank. Each vent will be in fuel during some attitude. If the first vent were to be used inverted, the pressure from the fuel would prevent air from flowing into the tank in sufficient volume. The same for the second vent when inverted.

Alternately, if there is enough manifold sticking out from the engine (generally on the top or bottom of the manifold), you could tap it and install a pressure tap.

I hope this makes sense.