How tight is too tight...

[YeLLowBoaT]

I just gaped out my 12jc, at .019( .020 won't fit and .018 is lose) I know .025 is supose to be perfect. The pump has not been run in about 18 years so I am going to replace the packing seals/gaskets/o-rings. And most likly the barings. Now should I ship off the impeller and ring to get machined or just run it? Its a AL impeller some where between an "A" and a "A/B"

[Oldsquirt]

What clearance were you measuring???
If the clearance you measured is between the front of the impeller and the suction housing, then you would add a shim in front of the impeller, on the shaft, to increase the clearance.
If you are going to go through the pump and replace the thrust bearing( I certainly would after 18 years of sitting), then you should wait until you are reassembling to recheck and adjust that clearance.