I need to tap the exit airhorn for the installation of the methanol nozzle.

I got the 1/8-27 NPT tap, but finding the right bit and how deep to go has been a challenge.

Is it a 11/32nd or 23/64th bit? How deep does one run the tap?!

I am mechanically inclined, just have never used one of these tools before.

I think:
1. Drill small pilot hole.
2. Step up bits to proper size achieved
3. Run tap in through (not all the way)
4. Clean burs
5. Repeat 3 and 4 until the nozzle threads on and snugly.

Done.

Does this sound about right?

 

You can drill a pilot hole if you want, but the 1/8"NPT is small enough to center punch and use the drill size. The package the tap came in should have the drill size, I know it's "R" but I think 11/32nds will work.
How deep to thread the tap will depend on the fitting you are using, remember that pipe thread is tapered so you want it tight before the fitting bottoms out.

 

yeah, the punch was included, but seemed like a bad idea to use on the intake horn, even though I am removing it to tap.

I guess I will get a better look when I get it apart.

 

You can also follow your drilled step holes with a taper pipe reamer which will give you the correct tapered hole before tapping. It's the best way.
Steve

 

You should tap it part way, hand tighten the fitting you want to put in, check how far it goes in, and repeat this until there are about 3 threads visible on the fitting. That is as deep as you should tap. Then tighten the fitting up with a wrench and use teflon tape on the threads for a good seal.

 

Ok for anyone who ever needs to do this:
Since I tapped the intercooler outlet, I first filled the inside with a towel to help keep debris out of the intercooler.

I took a 1/8 bit and drilled a pilot.
I then took a unibit and steped it out to one bit smaller than 11/32
I then took an 11/32 bit and drilled the hole out.

At this point I got out the 1/8 NPT tap and dipped it in oil, then proceeded to screw it in, then out, cleaning the burrs as I went.

I repeated that step going deeper and test fitting the nozzle till I got it where I needed.

So simple it hurts

Thanks to everyone who assisted me