Hi everyone, I am getting rady to tap the banjo fitting with 1/8 npt but I don't know what size drill bit to use (the tap does not specify). Also what should I use on the threads to seal them? I have heard to use permatex #2 and loctite 545. What do you guys think?

 

Look up the post by infidel for the fuel pressure gauge install. It is very good.
It should help. Use Permatex 2.

 

The pipe taps , and pipe threads in general are tapered , so using any drill bit that is big enough to get the 1st few cuts started into the hole is what you need .
As apposed to using a larger bit , and then the threaded hole will be lose .
When you get the tap going , pull out every so often , and check the fitting you want to put in , you should go about half way up the threads of the fitting [ hand tight ] with enough left to tighten with tool .
I use teflon tape , but make sure that the tap is not near the beginning of the threads , so to let any teflon into the pump , also about 3+ layers of tape .

 

For 1/8" NPT, a letter R bit is what you want. Failing that, 11/32" will work just as well.

I use permatex thread sealant, in the white tube. Not sure the number on it. I would avoid tape, last thing you want is an errant strand getting into your fuel pump. Use the sealant, keep it 2 threads back from the end of the fitting.

 

vulcan performance can hook you up with some fittings and hose to run to a pressure sender. Infidel's setup tips were also very good.
Youll need a snubber valve of some sort. Whether it is a restriction in a fitting or an adjustable valve.

 

Drill 21/64" for 1/8" NPT tap. But, do not drill all the way through the whole bolt, once you go through the bolt head - the drill bit will open up the threaded portion, you don't want to weaken the threaded portion. Once you're through, stop and tap.
P.S. You will have to use 1/8" NPT bottoming tap or make one out of regular tap by grinding off 1/3 of it. Full length tap will not work, it will not cut deep enough before it sticks in the threaded part of the bolt.

 

This is true for a 12mm banjo bolt. If you do it on your IP inlet banjo, which is 14mm, you won't have that issue. In fact, the drill bit is just a hair smaller than the hole in the banjo, so flip it around and drill the head out from the bottom of the bolt. Then you your its gonna be pretty close to center, and quite straight.