My Latest Carburetor (q-jet guys will get a kck out of this)

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

I'm still amazed. In fact the only carb I ever saw without a ported vacuum tube was a 1967 2GC, and I added a tube myself by drilling into the base at an angle and coming out just above the throttle blades (which is all ported vacuum really is anyway) and pounding a tube into the hole.

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Yeah I was too, that's why I never even bothered to look to see if it had one, I just assumed they all had ported vacuum, lol. Looking through my stash of carbs I have three or four more that lack ported vacuum as well. Some were CCC carbs and the other were late 70's or 1980 carbs, very odd to say the least.

 

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

are these not ported vaccum tubes on the front of your carb?...

 

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

The only way to tell if it "should" be there is to trace the vacuum passageways inside the carb. You can't drill a curved hole, so the passageways are straight, and if a change in direction is needed, another hole is drilled which intersects that one, and the end is plugged. Manifold vacuum ends up at the base of the carb either below the throttle plates, or elsewhere open to the intake manifold. Ported ends up at a hole or slot just above the throttle blades. Don't confuse the ported vacuum slot with the off-idle discharge slots. It is unusual to not have ported vacuum, since EGR and vacuum advances used it up to CCC carbs.

 

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

the lower one to the right in the picture is described as a ported vacuum source in diagrams I have seen and I've seen pictures of carbs with that source being used for the vacuum advance on the distributor...Oldsmoletick is calling it a timed port, that is the same as a ported port isn't it?

 

[Bonnewagon]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Yeah, it's the same, timed-ported, as long as there is no vacuum at idle, and the vacuum rises in concert with throttle opening. Now, I have seen the ported tube on either side of the front and at different heights depending on application. That's why it pays to test all ports/tubes with a vacuum gauge to see exactly what is what. Also the wrong throttle body or even the wrong gasket can upset the vacuum distribution.

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Ok, now I'm all sorts of baffled......Last night I decided to tinker with my timing a bit (no I still haven't put a light on a stock one yet, 😳 ), got out the vac gauge, got the jeep up to temp, hooked up my light, went to hook up my vac gauge, low and behold, the port I had been using for this purpose has switched to ported vacuum . I'm not nuts, the picture pontiacgp reposted:

are these not ported vaccum tubes on the front of your carb?...

The tube to the right side (rh meaning as you see it on screen, lol, technically lh side of the carb though :lol: ), is the one I have been using all along for hooking my vac gauge to, and was using for my vac advance, always had full manifold vacuum. So switching over the throttle plate put that tube to ported vacuum . Go figure right? lol. So being that, one port changed, I guess I should go back through and see if my others have too...

 

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

your q-jet is alive... :shock:

 

[Oldsmoletick]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

Now if I could only teach it to adjust itself :lol: . This might be why many people get frustrated with these things, little goofy things like what happened with mine, minor unseen differences that make a big change (btw I find it hilarious).

 

[pontiacgp]

Re: My Latest Carburetor (q-jet guys will get a kck out of t

the only way I can think it was manifold vacuum at idle if the throttle plate was open for some reason...Mark should have the answer for this tho...