Originally Posted by
abellringer
A little more info regarding tap fitting; I wouldn't advise reducing the tap unless you can fit it into a lathe and set the correct taper angle on the top slide; even then you are probably talking of microns of removal, as even a tiny reduction in size moves the tap a long way in the housing; emery or anything non solid could produce a ''wavy'' surface, also most likely produce tiny grooves and ruin the tap. I have correct reamers and paste plus bore gauges, so I am able to repeat factory processes. The factory grinding paste is ''CHEMICO'' valve grinding paste, in a double ended tin of coarse and fine paste; from the County Chemical Co. Chemico Works Birmingham. Probably no longer in existence as the tin is dated is dated 1949.
abellringer