'48 Fuel Selector Valve Questions

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'48 Fuel Selector Valve Questions

Post by oldtrucksrule »

I have a 1948 170 SN 18549

The airplane has been in my family since 1989. My IA has issue with the fuel selector valve "feel". It also has a little blue staining as well.

My question is what the fuel selector valve should feel like when switching between tanks. I've always been content with the feel of the valve. It's not a new airplane and should it feel like newer fuel valves? (ie smooth operation with defined clicks between selections?)

I believe the part number I'm looking to repair is 0511122. I have a call into McFarland about the availability of the valve and repair kit.

Thanks, Cory
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Re: '48 Fuel Selector Valve Questions

Post by GAHorn »

The above valves are actually identical brass plumbing valves originally mfr’d by Kohler, later by Weatherhead. This valve “feel” varies…from indistinguishable to having a tactile “click”…but not a particularly definite “detent” which later valves have. (Your A&P might be more familiar with the later aluminum-block vavles which have a more definite detent…which may be why he is questioning it.)

If yours works well, can be placed into position without great effort and does not “drip”…. then you have one of the better examples and it should probably not be messed-with. (However, lack of internal lubrication can make them stiff and eventually they will score and “gall” and then problems truly begin. Disassembly and lubrication with “fuel lube” or “EZ-Lube” is a good repair…but pay CLOSE attention to the arrangement of internal spacers and springs to be certain you put it back together properly.)

This brass “weatherhead” valve has a modern version which Spruce sells for “experimentals”… i.e., non-certificated airplanes. It is almost identical to the original, except instead of a brass “cone” inside it has a synthetic cone which does not bind even with no lubrication. The PN6749 (3-port) Spruce version also will not allow a “ both” position unless it is modified slightly by drilling “straight-through” that plastic cone to complete the “both” capability. (Using a 1/4” bit which has been ground flat on the end to get rid of the point…so as to not split the plastic cone…similar to drilling plexiglas. This is not something you’d wish to broadcast if you do it, but it works perfectly. The end-result is virtually indistinguishable from the original part …the only detectable difference being the slight increase in length of the handle-shaft.)

https://www.aircraftspruce.com/catalog/ ... ey=1957824

This valve is also common to the marine/boat industry and works on all fuels including ethanol-laced mo-gas.

McFarlane used-to “overhaul” these valves but check with them as recent inquiries I’ve had indicated they did not have the parts.

The valve below is the later, square “aluminum-block” valve which later B-models and early 172’s shared (and which articles in these forums have cussed and discussed.) For which McFarlane sells an inexpensive “kit” consisting of O-rings and packings to repair.

Here’s a pic from the B-model IPC which compares the two types valves… after 170-B Serial 20285 the 0513120-5 “aluminum-block” valve was used:
'53 B-model N146YS SN:25713
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Re: '48 Fuel Selector Valve Questions

Post by sfarringer »

As George stated, that tapered brass cone in a tapered brass bore of the early fuel valves can give trouble when the lubrication disappears.
Mine started getting stiff to turn, and it is something you don't want to ignore since it controls your fuel supply.

It is a bit of a nuisance removing and reinstalling the valve, due to access limitations.
But I think keeping it from deteriorating is worth the trouble.
Ragwing S/N 18073
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