1968 smog manifolds

[fireZ]

Anyone know the thread size for a smog fitting on a 68 Z. I need to run a tap through to clean up my thread to put smog tubes in.

[Boston14]

Check this post;     http://www.camaros.org/forum/index.php?topic=7067.0   



boston14

[fireZ]

I can not seem to pull it up on the site

[Boston14]

I didn't know how to insert it as a link ....... just copy it and paste it in your browser and that will take you there.

[Gramps69Z]

  Try this one.  http://www.camaros.org/forum/index.php?topic=7067.0

[acelr8]

1/4 Straght pipe not taper pipe is correct.Jeff

[169INDY]

I just went thru something similar.
One of the A.I.R Trees rotted out from the inside and required replacement.
Twisted off two of the 4 nuts and had to machine out the thread (Nut) while not intruding i.e. damaging the manifold.
I used a series of drill bits up to the correct tap size and pulled the 'treads' of the nut out of the manifold holes,,,
then purchased (appx 40$ ouch) a 1/4-18 NPSF 4FLT STR D/S Pipe tap from Fastenal (pn 16356 Brand Greenfield Tap & Die) and chased my manifold thread for a clean fit on the new tube nuts.

P.S. also machined some custom hidden plugs that seat below the tubes as my pump is de-vaned and need to seal exhaust gases from the check vlv etc.

Jim

[JohnZ]

P.S. also machined some custom hidden plugs that seat below the tubes as my pump is de-vaned and need to seal exhaust gases from the check vlv etc.

Jim

You can also use #10 x 1/2" flat-head machine screws in the holes in the exhaust manifolds (after knocking out the stainless tubes) instead of having plugs custom-made; the air manifold tube nuts then tighten down to the same dimension as if the tubes were still installed.

[169INDY]

You can also use #10 x 1/2" flat-head machine screws in the holes in the exhaust manifolds (after knocking out the stainless tubes) instead of having plugs custom-made; the air manifold tube nuts then tighten down to the same dimension as if the tubes were still installed.
[/quote]

Ya, I have even heard of folks suggesting (I would not) installing roofing nails to block the passage. Not very durable in my opinion.

I removed the tube, extensions. Machined (On a Lathe I have) a tight tolerance -plug- with shaping to really seal it up good. The "head" height was calculated to acquire the same standoff distance on the smog air manifold tree tube nuts. It was fun making CHIPS! The plugs do not intrude into the exhaust manifold chamber area at all.

[JohnZ]

Ya, I have even heard of folks suggesting (I would not) installing roofing nails to block the passage. Not very durable in my opinion.

I've done lots of them using stainless steel machine screws - they'll last forever, and won't corrode in place.

[169INDY]

Pic post: Pic of smog plug fabrication.

[rszmjt]

3/16 blind trailer rivits inserted into the smog rails and rivited. They never move and seal up.