requesting help - smog pump tube plug

[izzy_Britton]

ok, so after putting new carb on my truck i have no need for the smog pump or the tubes that go to the exhaust manifolds.

each manifold has a single stainless tube screwed into the manifold which is routed by rubber hose to the pump. I was not able to get a wrench to fit into the small space to remove the fitting so i cut the stainless tube and fit a socket on it for removal.

I was able to unscrew the drivers side without issue.

however the passenger side was more difficult and the threads of the fitting stripped off.

does anyone know what size and thread these fittings are? they are not pipe thread. and as it stands now i am stranded at home 15 miles from the nearest auto parts store and i am hoping that i have something to fix it.

is the gaping hole in my exhaust manifold(s) going to cause any harm to engine if i drive it into town and home again? I am pretty stuck and could use some help and good luck.

-Izzy

[chengny]

The following is specific to the AIR type pipes. Those are the kind that are used with the shaped tubular stainless steel manifolds. Yours may be different.

Sometimes heat (an acetylene torch) is required to get the fittings out. But that's usually only if you want to reuse the pipes.

If you use a pipe wrench it won't slip on the flats - the fittings will either come out normally or the pipe wrench will crush them until they cave in on themselves.

One way or the other, they'll come out with a 24" pipe wrench.

As far as plugging the threaded holes in the manifold:

They sell plugs specifically for the purpose of eliminating the AIR /PAIR systems. Again, I don't know what your set-up is so can't say with any certainty what size you require.

If you have a hydraulic supply shop near you, take one of the removed fittings in and they will have plugs with the proper diameter/thread pitch.

Just buy 8 steel NPT plugs of the closest size that wiill still get in the hole and weld them up. That is the most popular method.


Don't worry about harming your engine while running without those plugs. Other than making a lot of noise, everything will be okay. You might even find that you get an increase in power due to reduced exhaust back-pressure.

Matter of fact, depending on the diameter of your exhaust pipes and whether you have cats or not, at idle your manifolds will be under a vacuum. Those open holes (while still making a lot of noise) will actually be sucking air in.

[Tx Firefighter]

I can never find the plugs so I wind up using pipe plugs instead. They don't fit exactly, but a small smear of JB Weld and tightening them modestly works well. If you don't get carried away with the JB Weld and smear it in places other than the bottom of the threads, it looks very sanitary.
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[BONUSCAB]

Originally Posted by Tx Firefighter

I can never find the plugs so I wind up using pipe plugs instead. They don't fit exactly, but a small smear of JB Weld and tightening them modestly works well. If you don't get carried away with the JB Weld and smear it in places other than the bottom of the threads, it looks very sanitary.
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I think this is your best bet. I'd avoid driving with the plugs out, there is a chance you could burn the valves.

[Tx Firefighter]

I believe its 1/4 NPT plugs. They basically screw in place but you can tell if you really reef down on them that the threads will strip. Lightly coating with JB Weld and a very reasonable cinch down and you're good to go once it hardens. There's very little pressure in an exhaust system so you don't need to seal it up to the same standard as you would an air compressor line or something.

If you're in a pinch and away from home, mash some aluminum foil down in there with a screwdriver or something. Just pack it as tight as you can. That will get you home.
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[izzy_Britton]

thanks for the info, i was just now considering the jb weld way myself.

the other problem is that these are not little plugs they are between 1/2 and 3/4, maybe 5/8? they are NOT pipe thread so a pipe plug will not work, I thought to just cram a 1/2 brass pipe plug in the hole but it fits freely.

I have also considered welding the hole in the fitting and then welding the fitting into the manifold but i am worried that the exhaust manifold to head studs/bolts will likely break and leave me further of s**t creek.

and lastly the plug that came out came out without any threads, so i will have to JB weld it into place without the option of tightening it with a wrench, so JB weld will be the only thing holding it in place. I dont know how good that stuff is, i have never used it on anything that needed to stay put, with any heat, or any pressure, i have a feeling it is gonna fly out of there at the exact worst place. I better order up some headers and plan to not have the truck for a week or so while i extract exhaust manifold head bolts and studs... gah, this thing is snow balling on me.

-Izzy

[Tx Firefighter]

No one said they were pipe threads.
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[izzy_Britton]

Originally Posted by Tx Firefighter

No one said they were pipe threads.

I know this, and i was not arguing, not really. as it turns out the threads are a pipe thread of sorts. it is actually (according to the local auto parts expert) a tube thread. 5/8 tube thread.

so as it turns out 1/2 pipe thread plug is to small and a 3/4 pipe plug is to big.

I found a brass 5/8 'flare' fitting plug. because it is a gas flare fitting, the flare is protruding from the plug which is opposite of the exhaust manifold, i had to cut the protruding flare off.

The threads are still pipe thread which of coarse is different than the threads in the hole. but with a liberal mount of JB Weld and a big wrench i was able to thread it in place and get it all tight. Once the JB Weld sets in about an hour i will fire the beast up and make sure the plugs dont pop out.

Thanks for the help! hopefully problem solved.

-Izzy