Hi, fellow rotary enthusiasts.....regarding
the water hole just under the oil filter on my 1989 13b (which normally
would go to the heater core), I did some measuring. The hole measures .670".
According to the tap/drill charts, a 1/2-14 NPT tap should have the hole
drilled to 23/32", which according to my calculations, is .718". The difference
between the two is only around .048". I'm thinking it will be fairly easy
to open this hole up that small an amount, and tap it for a 1/2-14 NPT.
I'll keep you informed of my success or failures. Paul Conner
That's good news Paul, I plan to do that mod eventually...