Hey all, coming from my manifold vacuum port (behind the carb on the manifold) I have a brass plumbing fitting (90 degree) that goes to a brass T which then goes one way to a nipple for the hose going to my PCV valve, and then the other end going to a nipple for a vaccum gauge inside the car. I took the brass fittings apart today and found oil inside, and in the oil was this small part, looks like some sort of jet. I am curious is anyone can tell me what it is, and how it could have gotten into the vacuum line. It is about 6mm long and 4mm in diameter, threaded halfway up with a slot for a screwdriver. There is a small hole through the center (sure looks like a jet to me).

I have been noticing pretty poor gas mileage, and thought after finding this, if it is a jet, that would explain it. The carb is a Holley 3310VS.

Hope you guys can help me!
Thanks
Brad

brad,
Not knowing any other details on your engine or car, it looks like a restrictor that someone put in the line to either slow down the "action" of the vacuum gauge, or if it was in the pcv side, to cut down on the amount of flow through the pcv valve. Either way it would have nothing to do with gas mileage, but the fact that it had oil in it is not a good sign. Either the pcv valve is not in a baffled hole in the valve cover, or the engine has a lot of blowby, causing oil to be forced up through the pcv valve. How about a picture or better description of the pcv system plumbing.

Here is a picture of the setup, but your suggestion that it could be a restrictor for a vacuum gauge might be right. I used to have one of those screw on jegs/summit brand ones, but took it off, and this unknown piece was right where that gauge screwed on. I can't check now, but I will check tomorrow on that.

Thanks
Brad

Might be trying to limit the pcv vacuum for additional vac to the power brakes, maybe.
You didn't say if the car had power brakes.
Or like the previous thread : to keep oil blow by from getting through the carb, which is easy enough to check.

RandyB.

The car does have power brakes, they are being run from the vacuum port on the back of the carb. I am the one that hooked up this system, so unless this fitting is part of the pcv valve, then I certainly didn't put it in. One thing though, there was no part number listed in any of the catalogs here for the pcv valve for my car, so I just picked one of the shelf that looked the same as my last one. I assume this could be causing my problem. Any ideas what valve I could use (like maybe a napa part number or something?) or what other cars would use the same one?


I am still going to check and see if that old screw in vacuum gauge I had on it is where this unknown fitting has come from.

Thanks again!
Brad

The "jet" is almost certainly a part included with your vacuum gauge. I have a different concern though: connecting a vaccum gauge to a PCV hose makes no sense. The PCV is a controlled vacuum leak, and the vacuum gauge would show greatly reduced vacuum from what the engine was actually developing.

You should re-plumb the gauge into a manifold vacuum port that supplies only "dead head" accessories--vacuum advance, trans modulator, etc, not open ones like PCV or the power brake booster.

I bet you like your vacuum readings much more afterwards.

Shurkey, thanks for the advice. Right now I read about 17 inches at idle. If I just connect the vacuum gauge to the manifold source it is on right now, where should I run my pcv valve to? I have the larger vacuum port on the back of the carb running to my brake booster, and then my vacuum advance running to one of the small manifold vacuum ports on the base of the carb, so would it be better to run my pcv off the manifold vacuum port that it is on right now and then connect my vacuum gauge to one of the remaining ports on the carb (or T it off the vacuum advance)?

Thanks for the advice!
Brad

well, I went and found that old screw in gauge and low and behold it the piece threaded right into it. Thanks for help guys!

Brad

On my car, the modulator and the power brakes are tapped into the manifold with a tee. The PVC is hooked to the carb. Vacuum gauge is tee'ed off the vacuum advance, which is hooked to the full time vacuum port on the carb. You should get the PCV off the manifold. It can cause the cylinder the runner goes to to run lean.

Thanks for the advice Pat, I will switch my lines around to have the PCV off the carb, the vacuum advance with a T to the gauge also on the carb (with full vacuum) and the brake booster off the manifold.

Thanks again!
Brad

EDIT: As I reread my posts I can't believe myself, all this time I had forgotten that the manifold port was manifold vacuum, not the full vacuum one. I feel a little stupid now, going out to switch things around right now.