Author Topic: Smog tube nuts replacement source?  (Read 3171 times)

KevinW

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Smog tube nuts replacement source?
« on: February 24, 2019, 04:45:20 PM »
So I am working on my smog systems, was able to get the original drivers side smog tube off without drama.



But the two center ones on the pass side are getting destroyed.  Still working with penetration and heat, but the fittings will have to be replaced :(

 

These manifolds are from Dec68/Jan69 range.  Everything I have read is 1/4"-18 NPSF, but the threads are NOT 18, they are 20.  Plus I think they are steel, not brass? So anyone have a source?  I did think about buying a plug set and just drilling out the center of two of them.

Thx

169INDY

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Re: Smog tube nuts replacement source?
« Reply #1 on: February 24, 2019, 05:05:25 PM »
I am "thinking" the correct tap size IS 1/4-18 NPSF as I have repaired 1968 BB & 1966 SB manifolds using Greenfield tap & die # 16356 Type 5323 4 flute, straight D/S pipe tap as shown.

I used Heat & candle wax trick & a quality flare nut wrench with & without success.

JIM
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KevinW

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Re: Smog tube nuts replacement source?
« Reply #2 on: February 24, 2019, 06:15:01 PM »
Thx Jim, yes doing more research the 14"-18 is the one.  I was successful on 6 of the 8 using PB and heat cycles for a week, then slick 50 on the inside to lube the tubes. These two need more work :(

Stingr69

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Re: Smog tube nuts replacement source?
« Reply #3 on: February 25, 2019, 03:07:17 PM »
I would suggest finding a smog tree from some other less desirable (cheap) application and sacrifice it for the tree fittings.  You will obviously need to braze in some replacement pipes into your original trees.  It should come out great.

Try an oxy/acetylene torch and heat the manifold dull cherry red, Hit it with a spray of PB Blaster and you should be able to wrench out the fittings.  This method works magic on engine block plugs.

firstgenaddict

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Re: Smog tube nuts replacement source?
« Reply #4 on: February 26, 2019, 02:42:34 AM »
I am working on a couple of sets right now myself.
The individual tubes are silver soldered into the larger body from what I can tell.

You can get silver solder and flux but will need an oxy acetylene torch set up to get it hot enough.

By chance I have had experience with silver solder. The copper boiler for a carpet cleaner in a Cleaning van which an employee left full and froze, splitting the coil at the bottom. In the area where the propane flame directly contacts the coils.. The coils were $1100 so as a last ditch owner asked me...
I said we can try silver solder it is the only thing which will stand the heat.
It has worked for 5 plus years now in a direct propane flame. 

James
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Stingr69

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Re: Smog tube nuts replacement source?
« Reply #5 on: February 26, 2019, 02:47:20 PM »
Silver solder is probably the right way to reassemble the trees. 

The Oxy/Acetylene torch is much hotter than propane and should work much better for getting the fittings out. 

red69

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Re: Smog tube nuts replacement source?
« Reply #6 on: February 26, 2019, 03:37:39 PM »
I clamp vise grips on the tubing wrench to help keep it from spreading apart. Often helps on a tough fitting.

z28z11

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Re: Smog tube nuts replacement source?
« Reply #7 on: February 27, 2019, 04:59:35 AM »
If you're replacing the two male threaded pipes anyway, take a Dremel cutoff wheel and cut the tubes off to free the remaining smog tube assembly intact. Let your PB Blaster soak overnight from both sides of the fitting (shoot it back into the extension tube underneath). Then use a good quality 6 point socket to back the nuts out - carefully. Too much torque and you'll snap them off, forcing you to drill out the remains of the nut. I have used the successively-larger-drill-diameters routine until you can pick the thread remnants out - a painstaking process, but worth doing to save the integrity of the threaded port. I only use the tap to chase the threads after clearing, not to drive the remnants out. Just take your time, don't rush it, and think about what you're doing before getting frustrated with it. Derned things are too expensive to fix or replace - that's why you're doing this, right ?

Regards,
Steve
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Hans L

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Re: Smog tube nuts replacement source?
« Reply #8 on: February 27, 2019, 04:25:48 PM »
I sent my smog tubes to Jerry MacNeish who restored them back to perfection (stripped nuts, straightened the bends, new olive plating).  Turned out great!   
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