shosovr

Trying to figure out what was the original purpose of the 1/2" diameter metal nipple on the LT-1 throttle body that is located slightly above and to the left of the Throttle Position Sensor, and above the nipple that goes to EVAP solenoid. It had been capped off (it was that way when I bought my Camaro), but the rubber cap has dry rotted and come apart.

My Camaro is Supercharged and I feel that it should be making more boost than it currently is. Someone pointed out the deteriated rubber cap and said that it was the culprit of why my boost level is not as it should be. I removed the throttle body to tap that hole and install a bolt rather than putting another rubber cap on it, but it does not appear that nipple is associated with the air flow of the throttle body. So what is the purpose of that nipple? Thanks In Advance.

white97T/A

In stock form there is a coolant passage that runs through the bottom of the throttle body. One of the free mods people would do is bypass the coolant passage through the thottle body, in an effort to have a cooler air charge coming into the intake. It is common for people to put vaccum caps on the pipe ends that were the coolant passage through the throttle body. If this is what you are talking about if the caps were deteriorated it would not cause a drivability issue like you are describing.

For more info on what I discussed above do a search for "free mods" and "throttle body bypass" and you should find some detailed write ups and pictures of the process and you will know for sure what you are looking at.

shosovr

I have done a search on the "throttle body pass", which my Camaro has had done, but those nipples are a smaller diameter and located on the lower part of the throttle body. The one that I am referring to is located on the upper part. Thanks For Information Though.

shoebox

That large pipe up top is going to be the air feed to the valve cover for the stock PCV system.

97Z4CZ28

If I am understanding you correctly that is a long hose that goes from the TB to the rear of top of the pass. Side valve cover. Crankcase vent hose.

97WS6SCharged

Essentially correct except it's not a vent. It feeds metered air into the crank case to allow the PCV system to function.

Injuneer

It is designed to flow both ways. With a healthy PCV system, and limited blowby, it supplies air to the crankcase. But if the blowby exceeds the capacity of the PCV system, the pressure will be relieved through the hose into the throttle body. An unfortunate side effect of this happening too often is a buildup of oil in the hose, the throttle body, and eventually the intake manifold.

shosovr

Thanks For All The Information ..... SERIOUSLY !!! Sometimes it is difficult to know what all has been altered on a car, when you buy one that has already had some work performed on it. With my new found information (Thanks Guys) the rear passenger side valve cover which I now believe connected to the metal nipple that was in question, has a hose that connects to an aluminum catch-can with an Air Filter mounted on top. I have a BBK throttle body and that nipple does not "appear" to have any connection with the airflow of the throttle body. From what I can see, it leads to a hole opening inside one of the threaded mounting holes on the throttle body. ????? I don't imagine that I am losing boost from that open nipple, so I'll place another rubber cap on it (as opposed to tapping the hole and installing a bolt). THANK again for the information.

Injuneer

Here's the stock routing of the hose:

http://www.injuneer.com/images/photo.../DCP04254a.jpg

With the blower, I can see why they disconnected the line from the throttle body, because you would be pressuring the crankcase with boost. They probably revised the vacuum source for the PCV valve on the driver's side of the intake manifold. You don''t mention the year of your engine, and the stock routing differs from early LT1 years to later LT1 years. You need to add a "Signature" with basic info about your car - year, model, engine, trans and any major mods. That way it's easier for people to provide help that reflects the specifics of your application.

If the nipple is not capped, you are losing boost. If you are using the MAF sensor, you are losing air that has been metered through the MAF sensor, and that's not helping the PCM control the A/F ratio. There is an opening in the throttle body (at least the stock TB) that starts in front of the throttle blades, connects to a small chamber on the top of the TB, under the removable cover, and then to the nipple. I would put a vacuum cap on the nipple, and use a small band clamp like I have on the hose to prevent the boost from blowing the cap off.

shosovr

***Thanks Yet Again For The Information***. I have gained even more knowledge than expected. I AM still using the MAF sensor and would not have considered losing metered air. That may explain why my Camaro ran great after I had it tuned, but since would kick out black smoke on hard acceleration (more than usual). Hopefully capping the nipple back off will cure all of my woes. I have tried to ad a "Signiture", but not sure if it was excepted.

97WS6SCharged

Rubber caps work as a temporary solution but you'll need to clamp them down to keep them from blowing off under higher boost pressure. This leads to them cracking and breaking. I tapped and plugged mine permanently not too long ago. Looks much better.

shosovr

I have to admit that does look much better. Guess I'll do the same, especially since I still have the throttle body removed. Thanks.