Anyone know what size thread this fitting is?

[Hindsight]

On the side of the intake manifold there is a big fitting that has threads on one side and a 3/8" barb on the other. The brake booster hose connects to it. Since I won't be using this barb for power brakes, I want to use it to connect a hose to my blow-off valve but I need a slightly smaller barb and don't want to have an ugly reducer coupler so I wanted to replace it with a smaller barb. The only issue is that I don't know what size the threads are. It looks like a tapered thread of some sort and being a Japanese car, I'm pretty sure it isn't NPT. Does anyone know what it is?

Pic:
44127

Edit: Might be just easier to swap out the barb on the BOV with a larger 3/8" one and call it good.

I think the fitting is BSPT..... not sure of the size though.

[billjr212]

fairly certain it is this based on my order history on McMaster Carr: http://www.mcmaster.com/#2617k46/=yc1urn

1/8" BSPT

You may want to sense check me on that though.

[RM1SepEx]

Nope, I just bought a brass pipe fitting for it, too big by a whisker! I chopped off the nipple and welded it shut, screwed it back in. It is a metric pipe thread approx 10MM x 1 thread, very fine

I'm pretty sure that you could tap it to the std pipe thread and use the std plug tho

[billjr212]

Google confirms I am consistent: http://thefactoryfiveforum.com/showthread.php?14906-Vacuum-plugs-thread-pitch-confirmation

[Hindsight]

Nice! Thanks guys. I just need to either get a 1/8" BSPT to 1/4" barb or get a 3/8" barb for my BOV.

[Aero STI]

It's 1/8-27 NPT. I recently replaced the straight barb with a right angle.

[billjr212]

It's 1/8-27 NPT. I recently replaced the straight barb with a right angle.

Andrew - I'm guessing 1/8-27-NPT can be made to fit, not doubting that, but I can say with near certainty (the internet lets me do that) that it is 1/8 BSPT. Using NPT you will find that you muck up the threads if you ever need to remove it.

[RM1SepEx]

As I said, I just bought an 1/8 NPT plug in brass yesterday. It does NOT fit, I'm sure I could add a slight taper to the edge and make it fit but it is not the correct thread.

[Quiny]

I used British Standard Pipe Taper (BSPT) on all my unused ports, they fit very well, just a pain to find. Don't expect to go to Lowes or Home Depot and find them.

[Aero STI]

Andrew - I'm guessing 1/8-27-NPT can be made to fit, not doubting that, but I can say with near certainty (the internet lets me do that) that it is 1/8 BSPT. Using NPT you will find that you muck up the threads if you ever need to remove it.

Thanks for correcting me. I chased the threads with 1/8 27 NPT tap before installing the fitting and everything went together great. Looking at the specs between 1/8 BSPT (28 TPI and 55 degree included angle, rounded peaks) and 1/8 NPT (27 TPI and 60 degree included angle, flattened peaks), I can see how similar they are. The aviation gasket maker should keep things fully sealed. Oops.