Hello John, I have done it, very easy. Put an o ring under the cap, buy a radiator cap neck from a radiator shop, solder a cap on the bottom, install a nipple on the soldered cap, attach the nipple to the overflow pipe. Regards, Len Fanelli Abingdon Performance XPAG roller lifter cam kits Harley Davidson custom cams & gear sets 914 420 8699</HTML>