Imperial Fuel Valves

There are better, more modern valves than the old Imperials, but the new valves are expensive and they're not ORIGINAL so let's take a few minutes to fix up our old fuel valves.  There are three major problems with the Imperial valves: (1) they can "sieze" or lock up so you cannot turn the fuel on OR off  (2) they can leak in the Off position so that fuel runs through when you don't want it, resulting in a dripping carb or overflowing main tank and (3) most annoying of all is a leak around the stem which results in fuel dripping INSIDE the cockpit!

It doesn't take long to spruce up this old girls...take them apart by removing the handle and unscrewing the top, pull out the stem and spring.  There's a half round washer that will tip up when you pull on the stem.  It has a tab on the back side so you have to pull the tab out of its notch to get the washer free.  Clean everything using a toothbrush and MEK

Next you'll "lap" the stem into the tapered body of the valve.  There are special lapping compounds available, but most folks use toothpaste (a nice smelling mild abrasive).  Coat the stem with toothpaste (Photo 2) and then put it back into the valve body.  Use the handle to turn the stem back and forth in the body as if you're turning the valve on and off.  Do that a hundred times or more and the toothpaste will start to wear the stem and body so that they match perfectly.  Remove the stem and you can tell the lapping is working because the toothpaste has turned black.  Wash off the toothpaste to check lapping progress.  You're done lapping when the stem and body look nice and shiney.  Photo 3 shows a comparison of before and after lapping the stem.

Finally, re-assemble the valve using a new seal and fuel lube grease.  Newer (!?) Imperial valves use O-ring seals, just put a new one on.  But the older valves used leather seals which are no longer available.  I haven't tried this but people tell me you can use waxed dental floss or teflon string wrapped around the stem to replace the leather seals.