2536771 CAP 4BBL Intake Manifold Port Plug ?

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68 CUDA FORMULA S

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OK I thought I had this figured out but I was wrong. I can not seem to find the right plug to block off this vacuum port on this CAP intake manifold, the bigger one that is right behind the carb. Does anyone have a picture of what ever was in that port from the factory and does anyone know the proper size plug that can be used to block it off. Take a look and if you can help I would appreciate it.
Thanks
Bob

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My 67 non-CAP doesn't have that hole, sorry. Is it not the same thread as the vacuum nipple?
 
It's either 3/8" or 1/4" pipe thread. I cannot tell. Get both. They are cheap.
 
3/8" is too small, and 1/2" is too big. No one in this area carries a 7/16" pipe thread so I thought I ordered the correct one on line and it showed up today WRONG!!! just can't seem to find anything that will fit.
 
Interestingly my CAP 2536771. doesn't have the hole drilled or tappe and it looks from the underside that there would be no where for it to go if it were.

Just out of curiosity have you tried machine thread bolts?

intake top.jpg
Intake bottom.jpg
 
Huh, got me thinking. I have a manifold in the garage. It is a #563 (non cap) and doesn't have the passage cast in it. The manifold on my 66 is a cap intake and has a big headed (ugly) plug. No idea what size. This is the #771 off my 273.

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doesn't look to be a vacuum port. Ported into crankcase but for what? More PCV?
Oil drain for those upside down applications? LOL
Could be that there is a oil pan plug that fits it.
 
Nope, I don't have a photo of the underside of my intake for you. Sorry.
 
I picked up a standard 3/4" sae bolt today, it is just a bit smaller than the 1/2 pipe plug and it screws right into the port. I have a guy that is looking for a plug that size with an o-ring on it because if you look at the top of the port you can see the small embossed area, a flat washer type gasket I don't think would seal it off. If he does find the plug that I need I will take a picture of it before I install it and list the size for anyone else who is going to have to go through this.
Bob
 
I don't see the hose but it looks like the power brake hose goes there. Not for sure.

273 view.jpg
 
see the hose but it looks like the power brake hose goes there
Logical, but why make two castings one with a port and one without, i mean mine has no way to get to the runners and the casting looks like they had a swappable mold from the bottom side.
 
Logical, but why make two castings one with a port and one without, i mean mine has no way to get to the runners and the casting looks like they had a swappable mold from the bottom side.
No Idea. They did some strange things with California cars. The carbs didn't have vacuum ports for power brakes back then I don't believe.
 
I just sold a 67 model 273 4V manifold that came off a CAP build. I don't recall it had a port drilled there. I'm assuming this problem child is earlier model.
 
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