R. -
What I have done many times in the past is to remove the butterfly from the shaft and pull the shaft out of the base. Drill and tap a small hole in the open end of the shaft. Get some Teflon "O" rings, which you can usually buy at an "O" ring supplier, the size of the shaft. Bore a slight recess in each side of the outside of the base where the shaft goes through the base. I usually use a countersinking bit for this and turn it on a hand held chuck. Slip a Teflon "O" ring onto the shaft, put the shaft through the base, and on the other end, slip a Telfon "O" on the shaft, put an oversized (larger than the "O" ring) metal (brass) washer over the "O" ring and screw the metal washer onto the shaft snug. Don't over tighten the washer, just snug. If the turning play in the shaft is too tight, bore the recess in the base a little to let the "O" ring recess a little more.
This will seal the shaft where it passes through
the base and stop your vacuum leak. It may not seal 100%, but it will help a bunch, especially if the shafts are real worn.
Good luck!
Joe
