# info needed on JH head vacuum port on the back of head??????



## xet33 (Mar 3, 2010)

I was deleting some vac lines a/c boost valves etc and there is a port on the head I have it capped off now which I think is correct if someone can confirm.


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## xet33 (Mar 3, 2010)

guess no one owns a gti on vortex


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## nbvwfan (Aug 15, 2007)

xet33 said:


> guess no one owns a gti on vortex


I own four
2 MKII's and 2 MKI's

The port on the back of the JH head is for the air shrouding.
Capped off, it may run decent, but may impact performance and economy (throttle tip in and idle).
You ought to connect it to a point after the throttle body.
That is what I have done on mine as I don't have a conventional setup and running ahead of the throttle body, (in the discharge stream) I had surging.


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## xet33 (Mar 3, 2010)

ok thank you for reply I can just pipe it direct into the intake manfold then?


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## nbvwfan (Aug 15, 2007)

xet33 said:


> ok thank you for reply I can just pipe it direct into the intake manfold then?


Yes.
I tapped it off a fitting I added at the support castings, but plumbing it after the throttle body anywhere will work.


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## xet33 (Mar 3, 2010)

but just so I am on the same page. from factory it was before tb correct.


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## Dr.Jeff (Oct 30, 2013)

I have a JH 1.8 GTI engine that came as a long-block...no intake, etc. on it when I got it. I want to install it in my early Rabbit, replacing the 1.6 (non air-shrouded) engine. Without knowing how all of the vac lines were routed on the 1.8, this fitting for the air-shrouded injectors is a bit of a mystery to me. Can anyone describe how it was plumbed on a stock engine?
Thanks, Jeff


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## volkshead83 (Feb 8, 2014)

You just need to make sure your using the correct injector seats. Or your going to be sucking all the fuel your spraying back thats coming from the injectors into the intake manifold. I believe it was actually used for cooling the injectors. Which is why they had caps and o rings on the tips of those injectors.


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## Dr.Jeff (Oct 30, 2013)

I found you can only use one type of injector holder with the air-shrouded head...the other types won't even fit. These are the injectors without the 'hat' on the tip ('83-'84).

My question is with the original configuration, where did the vac hose from this head fitting go to? The fitting is located directly between the 3rd and 4th injectors (on the head) and is basically a 'nipple' for a vacuum hose. But how is it tied into the rest of the system...what does the other end of the hose connect to when everything is stock?
I've searched but have not been able to find it in any diagrams, etc. It may be unique to the '83-'84 GTI's and the manuals do not show it.

Thanks, Jeff


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## nbvwfan (Aug 15, 2007)

volkshead83 said:


> You just need to make sure your using the correct injector seats. Or your going to be sucking all the fuel your spraying back thats coming from the injectors into the intake manifold. I believe it was actually used for cooling the injectors. Which is why they had caps and o rings on the tips of those injectors.


Actually, _sucking the fuel into the intake manifold _ is sort of the point. They were primarily used to aid atomization and improve performance.




Dr.Jeff said:


> I found you can only use one type of injector holder with the air-shrouded head...the other types won't even fit. These are the injectors without the 'hat' on the tip ('83-'84).
> 
> My question is with the original configuration, where did the vac hose from this head fitting go to? The fitting is located directly between the 3rd and 4th injectors (on the head) and is basically a 'nipple' for a vacuum hose. But how is it tied into the rest of the system...what does the other end of the hose connect to when everything is stock?
> I've searched but have not been able to find it in any diagrams, etc. It may be unique to the '83-'84 GTI's and the manuals do not show it.
> ...


Thats not true, There are three types of injector holders that fit into the air shrouded head, whether everything will work is debatable
1. CIS non air shrouded Volkswagen - Rabbit, '77-84, including Pickup, ***except Convertible and GTI***
2. CIS early air shrouded, GTI
3. CIS-E/M late air shrouded and Cup,

If you have a non shrouded head, only #1 will work
If you have an air shrouded head, #1,#2,#3 will work
You might want to do some more research before trying to state things as factual, it may end up causing more confusion.

To the question you asked see below:
It looks to me that the nipple connects to a tee that runs between the Auxiliary Air Valve (19) and the throttle housing (13).









:thumbup:


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## ps2375 (Aug 13, 2003)

I actually had a digi cup that fit that head also. I had that port on my head blocked off when my motor was on CIS and on MS with no ill effects as far As I could tell. Car idled fine on either system and made good power and had excellent economy with any cam I had in it on CIS or MS.


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## Dr.Jeff (Oct 30, 2013)

In response to the reply by "nbvwfan", thank you for the info. The image you posted is a great benefit in answering my question. Item #24 is the fitting in question that mounts to the head.
However I have to take exception to your other comments:
1) Sucking fuel into the cylinder, not the intake manifold, is the point. When the intake valve opens, the vacuum directly from the cylinder (just below the injector) is greater than the vacuum at the plenum portion of the intake manifold. Therefore the fuel and air (from the shrouded injector holder) are drawn into the cylinder (in addition to the air from the manifold). That is how the air-shrouded injector arrangement helps to atomize the mixture...drawing additional air from around the fuel spray coming directly off the injector opening.
2) I have both types of head, non-air-shrouded and air-shrouded. And I have all three types of injector holders. While I never stated my information as "fact", I am relating my experience with the parts I have. The injector holders are NOT interchangeable between the heads...they simply do not fit the opening in the head other than the type they were intended for. The heads and injectors that I have are from '84 and earlier (as I previously stated: Jh 1.8 GTI and earlier 1.6). Therefore I cannot say if the later heads, injectors, and/or holders are different than what I've stated. The reason I have all three types of holders is because some of our parts suppliers have incorrect information in their descriptions/web sites, and some Vortex members post erroneous information, which led to purchasing the wrong parts.
I do appreciate the help with the vacuum line routing, thanks.


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