My tap and die kit says for the 1/8" NPT tap, you want a 5/16" drill bit. Good luck, keep her lubed up while you go!

 

NPT is a tapered thread, so don't tap it too deep or you'll have problems.

 

Just curious why you don't use a vacuum line off the carb?
I have my vacuum gauge hooked up to the bottom vacuum port on my Holley since my Vic Jr. doesn't have vacuum port either.

 

Yeah, this is a good point, about 1/2 the cheap gauges we have come through the speed shop have a poor taper job cut on them and cause sealing/threading problems. Don't go too deep with that tap.

 

I always use an 11/32" tap drill size for 1/8" NPT hydraulic fittings....best way to understand proper NPT tap depth is to run the tap down an already threaded bung or port to see how far it goes before getting tight and cutting material, then mark it (tape works good) and use that as a guide for depth. I just use my eyes (tapping thousands of holes gives me a feel for such things *G*)...

If tapping aluminum, I always use special tapping fluid for non-ferrous metals or kerosene...

 

The back port I've got going to my pcv valve, and the front one I've got hooked up to my elec. choke. I know I could probably remove it.

 

Thanks. It is an aluminum spacer plate that I'll be tapping. Well it looks like it's off to the hardware store for some kerosene.
Thanks

 

Just remember, if using kerosene as a tapping fluid, to just drizzle it onto the tap as you're cutting and to make sure the area is well-ventilated and away from standing pilot lights...

Most folks use the non-flammable, non-toxic, politically correct tapping fluids but I'm somewhat of a rebel..*G*

 

In other words, I should take up smoking... =^)