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Smog hole in the manifold needs repair 1968

 
Old 04-28-2019, 08:00 PM
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cor66vette
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Default Smog hole in the manifold needs repair 1968

I posted this in "General"- maybe it's better addressed here.


In an attempt to plug the smog holes in the manifolds, the previous owner had run a bolt all the way through one of the holes, and past the"lip" that retains the exhaust tube extension, and now that hole is without its lip. Has anyone dealt with this problem and made the necessary repair? Thank you.
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Old 04-28-2019, 08:37 PM
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kossuth
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A picture would help if you can provide.
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Old 04-28-2019, 09:00 PM
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Originally Posted by kossuth View Post
A picture would help if you can provide.
Not sure these show what I'm talking about.


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Old 04-28-2019, 09:35 PM
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Are you planning on having your smog system function correctly when reinstalled?
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Old 04-28-2019, 09:40 PM
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Are you worried that the bolt won't seal if there isn't a lip to seat against?
Maybe use a short bolt with some hi temp anti seize and torque it down tight so that it seals against the bottom of the bolt head.
I used standard pipe plugs, which should have a tapered thread as opposed to straight threads on a bolt, on mine. Then ground them off flush with a peanut grinder. They now look like undrilled bosses.
Just looked at the post above. Putting on the smog tubes or deleting?

Last edited by Sayfoo; 04-28-2019 at 09:42 PM.
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Old 04-28-2019, 09:53 PM
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Originally Posted by Tooch1 View Post
Are you planning on having your smog system function correctly when reinstalled?
I wasn't sure, but at this point, I'll settle for it being non-functional, as long as the smog tubes can attach without leaks. If I run across a deal on replacement manifolds, then I might change 'em out.

Originally Posted by Sayfoo View Post
Are you worried that the bolt won't seal if there isn't a lip to seat against?
Maybe use a short bolt with some hi temp anti seize and torque it down tight so that it seals against the bottom of the bolt head.
I used standard pipe plugs, which should have a tapered thread as opposed to straight threads on a bolt, on mine. Then ground them off flush with a peanut grinder. They now look like undrilled bosses.
I don't want to plug the holes. I want to know if the threads in the holes, and the missing lip can be repaired, so the smog tubes can get attached. I'm told that without that lip the tubes won't seal.
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Old 04-28-2019, 09:54 PM
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Originally Posted by cor66vette View Post
Not sure these show what I'm talking about.


Gotcha... I am assuming you are putting the air stuff back on because you live in a state that smogs your car and the previous owner either didn't or didn't care about the smog stuff. If that is the case given that you said the PO has drilled and tapped the manifold for the bolt in question I would source a new or new to you manifold. That could be repaired but you'll go through more trouble than its likely worth.

Depending on what year your car is you can source a PAIR of NEW manifolds for about $200 or so off rockauto. Might find them cheaper still

Last edited by kossuth; 04-28-2019 at 09:58 PM. Reason: Price was incorrect.
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Old 04-28-2019, 10:07 PM
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You may be able to drill out the hole, tap, and install a reducing bushing. Some of them have a lip.
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Old 04-29-2019, 08:00 AM
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Originally Posted by kossuth View Post
... Depending on what year your car is you can source a PAIR of NEW manifolds for about $200 or so off rockauto. Might find them cheaper still
Originally Posted by Sayfoo View Post
You may be able to drill out the hole, tap, and install a reducing bushing. Some of them have a lip.
I'm going to try and save these manifolds. They're date correct for the car, so I'd hate to lose that, especially since the smog system is also date correct.
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Old 04-29-2019, 08:36 AM
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Braze the opening shut from the inside - would be worth a shot. You would only need to install the tree on the outside. No pan head screw required.
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Old 04-29-2019, 09:13 AM
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Originally Posted by cor66vette View Post
I'm going to try and save these manifolds. They're date correct for the car, so I'd hate to lose that, especially since the smog system is also date correct.
If that is the case I would pull the manifold and take it to a good machine shop. A previous poster recommended a bushing reducer with a sleeve on it, I would have the shop do exactly that. I looked before I initially replied if anybody makes a “repair kit” for such an issue with said bushing and I obviously didn’t find a kit but did find the cost of the manifolds.

If somebody can find a repair kit you can install yourself that would be great, but from what I’ve found it would have to be fabricated which means you’ll have some money wrapped up in it.
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Old 04-29-2019, 09:16 AM
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Originally Posted by stingr69 View Post
Braze the opening shut from the inside - would be worth a shot. You would only need to install the tree on the outside. No pan head screw required.
Not sure how much faith I would have in brazing given the proximity to the exhaust outlet.
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Old 04-30-2019, 09:24 AM
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Non functioning with no need for the extension tubes is the way to go. No need for a functioning smog system. If you must have it work, the bushing idea in that drilled out hole sounds like the best idea.
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Old 04-30-2019, 10:26 AM
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I think that lip is what the flared tube seats against. And without that lip that tube is never going to seal. So it's not really repairable for functional. it can be repaired so that it looks functional. You could probably buy some bushing with the correct inverted flair on the inside and a pipe thread on the outside. But then you would have to drill and tap to the very large pipe thread size and the bushing would be there and rather obvious. If you had to have working emissions this would be something to consider.

Last edited by derekderek; 04-30-2019 at 03:56 PM.
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Old 04-30-2019, 10:49 AM
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I'm concerned about leaks, though. With that over-sized hole, I don't know if the tubes can screw in securely. Once I have the tubes, I can test the treads and check for leaks. I was told that the threads on the tubes I'm getting are 1/2 x 18nf flat bottom- a stranger than strange thread size, in my case anyway. Of all the taps I have, I do not have that size and they're not cheap, so buying one for a one-time use will just add to the cost of this project, and my budget for this has already been laughed at. I'll try to borrow one for this job, and try tapping the existing threads and see how many OR IF any of the threads are good, and go from there.
Your comments are appreciated and understood, and it looks like non-functioning may be where this is going. If I decide otherwise, I'll put the smog system to the side, and try to secure a set of usable smog-ready manifolds.
I'll update this post with the outcome of these shenanigans.
Thank you all.
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Old 04-30-2019, 02:12 PM
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This should be the end result for your engine. Looks pretty and doesn't work. I actually had one hole in the R-side manifold damaged as your's.
Manifold trees were blocked, vacuum line to diverter valve blocked and vanes knocked out of the pump.
Again, if you are Determined to fix that drilled out hole, do as recommended by Sayfoo.
Here is the seal of the exhaust gas manifold to tree; tree tube flare to extension tube flare, the lip only serves to hold the extension tube in place.


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Old 04-30-2019, 02:42 PM
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^ ^ ^ Thanks for those pictures. With each new pic I see, I have a better understanding. The problem I see with the screw blocking the tube (your last picture) is that in my case, without a lip in the hole, that screw can fall out- unless yours is actually screwed in place in the tube. Also, how did you work around the damaged hole?
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Old 04-30-2019, 02:59 PM
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Your manifold looks pretty corroded, and might not seal if you had the correct parts- for restoration. Manifolds (non Corvette) are relatively cheap and available. Just replace this one and save for later.
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Old 04-30-2019, 03:06 PM
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^ ^ ^ The pictures do make them look pretty shitty, but they're actually not bad. If I have issues with the smog tubes sealing, then yes, I'll look for another set.
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Old 04-30-2019, 03:59 PM
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