A better way for blocking off unused vacuum lines!

[Talyn]

So I've never quite been happy with any of the usual methods of dealing with unused vacuum nipples.
Looping vacuum lines, or plugging vacuum lines with bolts add's clutter, looks crappy, and while unlikely can pop off, will eventually dry rot, if the bolt is too big might make it break prematurely. Then there are those vacuum nipple plugs you can buy at the parts stores that somehow dry rot to pieces in only a few months if not weeks. There's crushing the lines (what a previous owner did to my current DSM) which probably doesn't seal completely. And lastly JB weld or similar, which again looks like crap, and can fail. Also these last two methods are irreversible should you change your setup and need a vacuum source again.

So when I recently saw a vacuum distribution block on a parts site I had the idea to basically copy those.
I am going to attempt to remove the unused throttle body nipples, as well as the unused PCV nipple on the IM and then drill and tap those holes for NPT fittings, which are commonly available as nipple fittings or plugs, and commonly used when people need to tap a boost or vacuum line. I have an old throttle body lying around that I will test this on first, but if it turns out well, which I think it will, I would like to make this a sticky for other people looking for a better solution like I was. I wanted to do it this weekend, but unfortunately nobody seems to stock 1/8 NPT pipe taps, and I am pretty sure that is the ideal size for the TB nipples. I did order one, found one for $4 and change on ebay w/ free shipping, I'll be attempting this next weekend and come back with my results.

 

[totaleclipse_05]

Interested to see the results of your project!

 

[19Eclipse90]

A 1/8 NPT thread will be exceptionally large for the throttle body vacuum nipples. The nipples themselves only measure about .190" (roughly 5mm) in OD. A 1/8 NPT OD starts at about twice that, around 0.405". Then there's the minimum thread engagement that you need concern yourself with, I can't see there being enough real estate to do this.

 

[Talyn]

Isn't the 1/8 measured at the threads? I thought about doing 1/16, I wanted to measure the nipples, problem is my caliper is gone...Yet another thing I have to re-buy...
Where exactly do they measure NPT stuff at? Is it measured ID? Looking at the fittings, you are right, they are huge. But the vacuum block I saw used 1/8 plugs, so I thought that it would be OD, as I think a typical vacuum hose would be about 1/8 ID?

 

[Talyn]

I guess 1/16 from looking at this fitting:
http://www.summitracing.com/parts/aei-15630/overview/
I don't understand why the threaded portions are so much wider than they need to be. Is NPT measured in thread pitch or something? I just can't see how any part of that is 1/16 except maybe thread pitch...
And actually even that might be a little too big to fit, but I'll see what I can do with it, I want to make this work if I can.

 

[19Eclipse90]

Unfortunately with pipe threads, the "1/8" or "1/16" isn't designating any physical characteristic of the fitting itself. It is all based on a standard that uses and follows sizing for piping; see: http://www.engineeringtoolbox.com/ansi-steel-pipes-d_305.html

IMO -- and I agree with you -- 1/16 NPT would even be too large. I do know there are a couple pneumatic actuator manufacturers (Festo, for example) that use M5 threads for the fittings on some of their smaller units. The M5 set screws they use to block the "secondary" access ports have a little thread sealant on them and not much else to seal. Of course, I don't know how well they seal but they seal well enough to allow the actuators to operate as intended. Just some food for thought.

 

[Talyn]

I wonder if BPST might be a better choice? No time to look into it right now, but I'll look into it when I get a chance.

 

[19Eclipse90]

BSPT and NPT are nearly the same size. The main differences between them are the angle of taper, the thread profile geometry, and (sometimes) the thread pitch or number of threads per inch. See: https://www.valvesonline.com.au/references/threads/

 

[wishihadatalon]

In the past on my throttle bodies, I have removed the nipples and tapped them for m4 or m5 (I'd have to verify) set screws. I then coat the set screws in epoxy and thread them in place. I've never had an issue with leaking after doing this. Also the unused PCV nipple could be tapped for an 1/8"npt thread and plugged with ease.

 

[Talyn]

Well m4 and m5 aren't really designed to seal things, and they don't make plugs or barb fittings in that thread.

That being said, initial results are promising, 1/8 is too big, but 1/16 seems like it will work, I don't have a fitting yet to check if I went deep/wide enough. NPT is a taper thread, but I think it's wide enough. I really need to get another caliper so I can measure stuff like this.
To remove the nipples I just heat fatigued them by bending back and forth with pliers till they snapped, I've read that they can be pulled right out with a torch, but this was easier and quicker without requiring a lot of tools or heating something you probably shouldn't. After that I drilled out what was left, started out small, also have to be careful with your drill bits and go in spinning when drilling something that has a hole or you can break your bits, also try to keep straight of course. An 11/64 bit will finish off the nipple, will either grab it and pull it out, or if not you can bend the rest inward with a screw driver and drill through the rest of it. Then I used a 15/64 bit to drill the hole for the tap. There is a step in the back of these holes that you should try not to drill through, best way is to measure its depth and put tape on your drill bit, you can see that on the right side i didn't go through, but on the middle i did, but i was being lazy and didn't measure and tape, do as i say not as i do...I didn't have an arbor that fit the tap, but a 12 PT socket on a 1/4 ratchet works fine. I was worried at first about having enough room between the nipples, but there is still plenty. Will update again when I can check fitment of a plug or fitting.
And of course this is still a work in progress and not a full write up yet, and I'm not responsible if someone attempts this and screws up a throttle body, attempt at your own risk and all that. That being said it seems like it will work out nicely the way I had hoped.

 

[GST with PSI]

In the past on my throttle bodies, I have removed the nipples and tapped them for m4 or m5 (I'd have to verify) set screws. I then coat the set screws in epoxy and thread them in place. I've never had an issue with leaking after doing this. Also the unused PCV nipple could be tapped for an 1/8"npt thread and plugged with ease.

Yup, I've done the same thing to multiple TBs. It works awesome.

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[Talyn]

I think you guys are missing that a good portion of the reason I chose to use NPT was that if I need a vacuum source in the future I can simply remove the plug and drop a barb fitting in.