Working on a 270 that has a 3/4” drain hole installed in the block located forward of the fuel pump hole.
This was probably used for an auxiliary pump mounted to the motor.
I want to thread it, and install a plug. I am on a steep learning curve learning about taps, thread types, and how to fit a threaded pipe plug into this hole. For example: a 1/2” square end plug almost fits into this hole but it has a slightly larger diameter than 3/4”. I came to the conclusion that I need to enlarge the hole and tap it so the plug will fit.
1. What size of drill bit do I use? According to the link do I use the 23/32” or 57/64” drill bit?
http://www.carbidedepot.com/formulas-tap-pipe.htm 2.Do I use a tapered reamer before i use a tap to thread this hole? If so, what size? 3/4”?
3. What size and type of tap do I use?
4. Do I use several progressively larger drill bits to get to the final diameter from the 3/4” hole that is present?
Forgive my ignorance, but this is new to me, and I need to accomplish this task correctly.
Thanks. Tom
