Author Topic: '69 396 Smog tube repair  (Read 1211 times)

hihorse

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'69 396 Smog tube repair
« on: February 17, 2020, 04:16:03 PM »
Has anyone attempted to repair a smog tube end (at the manifold)?  if you were successful ,how did you do it?

169INDY

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Re: '69 396 Smog tube repair
« Reply #1 on: February 17, 2020, 06:57:59 PM »
They tend to ROT from the inside out, if your tube is a older as built in service one for years you would be amazed how thin and spindly they are, even just loosening the retention nut can twist a tube out of shape. I have had to just order replacements from Hodel and did a block off plug in the manifold and de'vane the pump to keep the look but not the function. The ends have a flare to them, but if you are inclined I would guess a possible harvest and braze graft repair is possible not sure how you could cover it up.
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

z28z11

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Re: '69 396 Smog tube repair
« Reply #2 on: February 18, 2020, 05:34:20 AM »
They tend to ROT from the inside out, if your tube is a older as built in service one for years you would be amazed how thin and spindly they are, even just loosening the retention nut can twist a tube out of shape.

Amen, I've removed a bunch of tubes over the years and found this statement to be true. Salvaged a few, you really have to be careful as the fittings seize on the tube itself and lock up - when you get the threads free in the manifold, you can spiral a tube quickly if it won't break loose from the corrosion bond between the tube and the nut. Kroil or PB Blaster soaked liberally beforehand help, slow and careful moves work best.

You can repair the tubes if you are handy with a TIG or MIG welder - source the proper pre-flared pipe end (brake lines) from your local parts store, find a smaller tube that slips inside the cut and sectioned pipe to support the tube internally, very slight chamfer to each side to allow weld penetration, TIG or MIG stitch on the lowest heat setting until you have the joint filled, and you're set to grind off the excess and coat the pipe. You'd be surprised how effective it is.

After all that, a better suggestion is to buy the best reproduction you can while they are still available. The '67-'68 small blocks are gone, nobody does them anymore - likely indicative of the shrinking market. '69 small and BB are the only first gens left, who knows how long they'll last.

Regards,
Steve
1968 Z28 M21/U17 BRG/W 1967 Chevy ll Nova SS 
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06  1949 3100 5wd 235/6

x66 714

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Re: '69 396 Smog tube repair
« Reply #3 on: February 18, 2020, 11:11:05 AM »
Once you get it repaired you can make it non-functional by deveining the pump, put a BB in the hose that goes to the diverter valve, & put clevis pins in the tubes. Remove the long tube that goes into manifold. The clevis pin will provide a working seat for the manifold. If it has a/c on your big block you will have to weld up the numbers 6 & 8. Mine have been this way for close to 75k miles..Joe
See America's First, Chevrolet

1968 Z/28 Corvette Bronze. Black Hounds Tooth. 02E Los Angeles born 3/13/1968 pnt OO. Purchased March 1976
1969 SS396 Yellow/Yellow 08E Norwood born 8/28/1969 pnt 76E. Purchased April 1981

hihorse

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Re: '69 396 Smog tube repair
« Reply #4 on: February 18, 2020, 02:58:26 PM »
thank-you, appreciate the experiences that are shared.

firstgenaddict

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Re: '69 396 Smog tube repair
« Reply #5 on: February 29, 2020, 02:26:59 PM »
I repaired the end of one tube on my survivor Corvette smog system. Used a brake flare kit did the first part of the double flare then flattened the flare instead of making it a 45 deg.
To flatten it I used a 1/2" dia tube with the side cut out and hammered the fitting against a brass block...
IT took MORE time than it was probably worth, however it is original only once.
James
Collectin' Camaro's since "Only Rednecks drove them"
Current caretaker of 1971 LT1's - 11130 and 21783 Check out the Black 69 RS/Z28 45k mile Survivor and the Lemans Blue 69 Z 10D frame off...
https://plus.google.com/photos/112392262205377424364/albums?banner=pwa

 

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