Vacuum line off intake manifold fitting

[Ryman023]

Sooo picked up a new project jeep and between the first time and the third time driving it in the yard something fell off, unhooked, unplugged... off the intake manifold fitting. Here's my quick research from digging the site and internet...
This is the valve on the diagram, aarow points to the empty side, just like mine is now:

Heres the part number detail:

Here is mine on the engine:

I cant find a loose hose, a missing cap, or anything around that it might have been hooked to. Its sucking in and making a loud hissing, wont idle at all. When i plug it the engine purrs smooth... My question, does anyone else have a 1975 v8 AMC 304 5.0L that can take a look and tell me what it goes to? Or as knowledgeable as many of you are, maybe someone knows off the top of their head. Thanks very much!!

 

[Joebronco]

Reload your photos. Broken links


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[Ryman023]

Reload your photos. Broken links


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[Joebronco]

Is your emissions hooked up? Vacuum booster line would be my first instinct.


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[Joebronco]

Is your emissions hooked up? Vacuum break booster line would be my first instinct.


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[cjTango]

Sounds like it may be the PCV valve for the crankcase.

 

[Joebronco]

Photo of entire engine bay would help


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[Ryman023]

Photo of entire engine bay would help


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According to the diagram the PCV is on the cab side of the carb, this is issue is on the fan side.

 

[Joebronco]

According to the diagram the PCV is on the cab side of the carb, this is issue is on the fan side.

I'm almost positive that that is a break booster vacuum connection point OR it's for your canister. I'll have to check my bronco diagrams.


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[Ryman023]

Remembering my first message that this is a new noise, literally out of no where, I can't figure out what fell off or plug was lost. I did find these two lines plugged up, neither could reach the fitting that's sucking in air

 

[Joebronco]

I've had the cheap plastic caps that go on the vacuum lines get sucked into the port in the past. Its also possible that the line was capped and the cap got brittle and fell off.

If there are no issues when it's plugged, cap that SOB and wheel it.


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[Ryman023]

It actually wont stay idling with it off! lol when I capped it she purrs. I was more or less curious the purpose and what it "should" be use for, or if anyone had one they could check and see where it goes. ingesting do any damage?

THANKS!

 

[Lumpy Grits]

Looking at the MC on the firewall, and the marks around it. I'll bet at one time that Jeep had PB, and that was the attachment point for the booster.
LG

 

[Joebronco]

Looking at the MC on the firewall, and the marks around it. I'll bet at one time that Jeep had PB, and that was the attachment point for the booster.

LG

Exactly what I thought. Then it was capped and the cap came off or got sucked in.


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[Posi]

The brake booster manifold port on a V8 is located at the rear of the engine behind the carb. This manifold source is in front of the carb.
This particular manifold vacuum source feeds emissions. Some V8's came with one port others came with two.

 

[Joebronco]

The brake booster manifold port on a V8 is located at the rear of the engine behind the carb. This manifold source is in front of the carb.
This particular manifold vacuum source feeds emissions. Some V8's came with one port others came with two.

Not on a 5.0 it doesn't.


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[Posi]

Not on a 5.0 it doesn't.


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This is a Jeep CJ forum your post has nothing to do with a 1974 AMC 304

The vacuum port shown by the OP isn't large enough for a power booster.
The 74 AMC 304 wasn't offered from the factory with a power booster
The vacuum source shown is for emissions.
The brake booster manifold vacuum source for AMC 304 and 360 engines are located in the rear of the engine.

 

[Joebronco]

Your statement was that v8's vac port is close to the firewall. That image was proof that what you said was incorrect. That is a photo of a V8 with a port up front...

The vac advance only has one port. You are correct, the 5.0 did not come with a port, that's why most articles I've seen have suggested creating a T at the main vac (like the OP's setup) similar to what other v8's do. Similar to what I have done in my 5.0.

Unless, as I had originally stated. The emissions have been fooled around with and the canister line was capped. But since there is an outline where the PO had put a booster, it only makes sense that was the tie in location.


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[Posi]

Your statement was that v8's vac port is close to the firewall. That image was proof that what you said was incorrect. That is a photo of a V8 with a port up front...

I'm not sure why you posted an obvious newer V8 engine that has nothing to do with the OP's AMC 1975 V8.
Anyone that owns a AMC V8 knows the vacuum source to the brake booster is located in the rear of the engine.
The OP's pic of the vacuum source in question clearly has the smaller ports and not the larger port needed for the booster.

Edit: 75 not 74

 

[dodrosky]

Plug the port. Won't ever run correctly with that size vacuum leak. Just checked a 73 amc shop manual and no such port on AMC 304 's that year. Could have been added for '75 or another manifold may have been installed. I have a 360 manifold on my 73 and no such port on it either. I don't know what year the 360 manifold is from. I have the original 2bl manifold in my other garage and will check it tomorrow if needed.