Cessna 120-140 Association

6643 wrote: ↑Tue Nov 22, 2022 7:32 am

tonycondon wrote: ↑Mon Nov 21, 2022 7:52 pm the only thing between the fuel valve and a dripping carburetor is how perfectly matched the steel needle and brass seat are in the bowl of carb.

That's pretty normal... The only difference is that today "normal" carbs use a neoprene-like material on the tip of the needle. Stromberg did, also, until there appeared a bad batch of needles (from parts unknown) and thereafter, the Stromberg neoprene tipped needle was forever damned.

The idle cutoff position of the mixture control probably helps too?

tonycondon wrote: ↑Tue Nov 22, 2022 12:53 pmThe idle cutoff position of the mixture control probably helps too?

Negative! It only cuts off fuel to the metering circuit. The float bowl will still overflow, through the bowl vent, if when the float valve fails.

Question was asked about paperwork above. Central Cyl is repair station and gave me paperwork/invoice stating inspections, parts replaced and that it was overhauled to relevant standards and signed off as airworthy.

Hello, I'm new to this forum and 140 ownership....so be catch up a bit, if I have a slow drip from the Stromberg Carb when the aircraft is parked and the fuel selector is NOT off, that isn't something to be overly concerned with? The previous owner had the carb rebuilt twice trying to get it to stop and in the end, it always started to drip again. Shutting off the fuel when parked, it never drips.

33n140 wrote: ↑Sun Dec 11, 2022 12:52 pm if I have a slow drip from the Stromberg Carb when the aircraft is parked and the fuel selector is NOT off, that isn't something to be overly concerned with?

No, because you should never park the aircraft with the fuel valve on. Remember, given enough time, every float valve will start leaking, whereas gravity has been shown to be 100% reliable since the beginning of time.

Another good reason is so if the engine accidentally starts due to a hot mag, it won't fly away by itself, in fact, if you shut the fuel off and let it idle until it quits, it won't even start accidentally.

Thanks John

Just to amplify JohnCs "after fuel selector off, idle until engine quits". About 50 years ago, my procedure was to just close fuel selector valve, thus no drip. However after preflight, I would verify mag switch off and then pull prop thru 4 blades, listening to engine sucking fuel at carb to prime engine. Fortunately, in all my 76 years of flying, I was taught to treat a prop with great respect, but you can't believe the SHOCK when the engine started on one of the "priming" blades!! The antiquated mag switch failed in the "on" position. Got a field approval to replace with an ACS switch. FWIW

FWIW. I shut down by turning the fuel selector valve to Off and wait for the engine stop, then mags and master off. I've been told that shutting down by turning the mags off first introduces unburned fuel into the cylinders and this fuel washes the oil film from the cylinder walls. A lot of my flight experience is with large radial engines (R-1820, R-1830, R-2800, R-4360). Shutdown procedure is always: mixture off, wait till the prop stops, then mag switches off.

I have the same issue. When at home plate I turn the fuel off at the same place on my taxi to the hanger. Timing works out good to run it dry. Doesn't leak when parked with the valve off.

Have noticed it started to leak out the bottom when priming. Time for a rebuild

tdragger wrote: ↑Fri Dec 16, 2022 7:12 amHave noticed it started to leak out the bottom when priming. Time for a rebuild

Out the bottom of what? This may be perfectly normal. (I never prime unless the prop is turning...)