MTFCA Forum

I purchased a new Brassworks radiator for the 23 Roadster, I attempted to use the old petcock from the old radiator but it was a bit to big for the new threaded hole, so ordered a new petcock from Lang's and it also is to large for the threaded hole. Has anyone else had this problem and if so have a solution.

Get a 1/8 inch pipe tap and tap the hole a bit further. Sneak up on it so that you don't go too far.

Another tip - put some grease in the flutes of the tap to catch the chips and keep them from falling into the radiator or onto the floor.

Thanks I was thinking that might be what I need to do. Do you happen to know the threads per inch on those fittings?

The thread pitch is 28 tpi, it's part of the standard for 1/8 pipe. A regular 28tpi tap won't work, regular taps are designed to cut straight sided holes. The pipe tap has a special taper shape so that the threads get tighter as you screw the fitting in, that's why you don't want to cut too deep.

Ok thank you for all this information, I understand about the tapering of the pipe tap now.