Exhaust Manifold Fitting Thread Size

[Mike Nance]

Does anybody know the thread pitch and diameter of Item #2 Cap Nut? I am trying to plug the smog port off of the exhaust manifold.

 

 

[John76]

Mike,

Is your air pump still installed? Is your exhaust manifold (or thermal reactor) still installed?

If you do not need these smog components then why not remove them, including the gulp valve, bracket and hoses?

Just a simple plug is hard to do because the slip ring is positioned to allow the pipe to be inserted into the manifold by about 3/4". If you want (need) to keep everything intact, simply remove the belt to the air pump.  The one-way check valve prevents exhaust from flowing back to the pump. Check the vacuum port on the gulp valve to make sure it is not leaking (very common) and creating a vacuum leak to the #1 intake runner.

John

 

[tech71]

I have heard that you can slip a penney inside the cap nut to cap it off?

Edited May 13 by tech71

[John76]

20 minutes ago, tech71 said:

I have heard that you can slip a penney inside the cap nut

Use only genuine parts from BMW ... not a Lincoln.

[Mike Self]

1 hour ago, tech71 said:

I have heard that you can slip a penney inside the cap nut to cap it off?

I believe it's a quarter--pennies made after 1981 are copper-coated zinc and will disintegrate from the heat and corrosive effects of the exhaust.  Quarters are nickel alloy and will hold up much better...

 

mike

[Mike Nance]

You guys are a hoot. I went with a nickel. Sealed it up temporarily. The nickel should hold until I find a cap. 

[stephers]

we use to use the coin trick as well but then, we also would braze the end of that nut over     easy to do with the coin in there

 

Thanks, Rick

[John76]

7 hours ago, Mike Nance said:

I went with a nickel.

That makes (4) more cents than a penny.

A cleaner option is to find a hex plug after removing the threaded bushing from the manifold.

There are three of these on the '76 49-state manifold.

 

 

[Mike Nance]

@John76 I wonder if the Hex plug is available. I'll check the OEM site for the plug part number. Thanks for the info.

[John76]

5 hours ago, Mike Nance said:

I wonder if the Hex plug is available.

Here's the part number:

 

[Mike Nance]

Sweet. Thank you for your help

[Son of Marty]

If you try to get the pipe compression fitting out of the ex manifold go slow use a lot of heat and penetrating oil between the cast iron and rust it is possible to break the manifold so again go slow.

[Mike Nance]

@Son of Marty I was thinking it was going to be easy. I should have known better. Thanks for the tip.

[Son of Marty]

Ah Mike you know it's never easy, but just be aware that cast iron has no give it just breaks.

[tech71]

5 hours ago, Mike Nance said:

I was thinking it was going to be easy

No hurry though, the 5 cent fix should hold up for quite some time.

Edited May 15 by tech71