carb problems

[bd]

The PCV valve is plumbed to manifold vacuum (if plumbed correctly), and is functional and purges crankcase vapor whenever the engine is running, whether at idle or 7000 RPM.  Absolutely, the PCV should work at idle!

12* advance is a lot of initial timing, plus the 6* of vacuum advance, because it's plumbed to manifold, is 18*, if I'm duplicating you.  I'm not surprised it won't idle down.  Experiment with the advance curve, but to resolve your complaint you may need to switch to a ported source - just for chagrins, try it and see what happens.   

On the brake booster, I disagree that disconnecting the booster from vacuum and plugging the line "should change the RPM."  As long as the brake pedal is stationary (not actively being depressed) and the check valve at the vacuum hose connection to the booster is good, the booster should hold vacuum indefinitely.  As long as the internal valves aren't being deflected, the booster is a sealed system.  If disconnecting the booster and plugging the vacuum line changes engine RPM, the booster is leaking either through its internal valving or the diaphragm is ruptured.  Either way, the booster would need to be replaced.  From what you've told us, your brake booster is fine.

Why don't you try this approach?  All at once, disconnect and cap EVERY vacuum hose EXCEPT for the PCV?  See what your idle RPM does and whether it drops where you want it.  Then reconnect each hose one-at-a-time to see if there's a primary offending vacuum circuit.

So, are you holding a wire or a spaghetti line vacuum hose?   

[Irish_Alley]

sorry thought you just pulled the brake booster line off and let it go didnt understand you just pinched it

[TexasRed]

Like I said, with the vacuum can disconnected or connected to port, It'll idle at 750 or so with the idle screw backed all the way out. A 383 with some cam should require a decent amount of airflow. I have to monkey a little with the mixture screws to get it to stay there and not pickup speed too much.

Most people run about 12 degrees of initial? Yes, it comes out to about 18 at idle. Total advance does not include vacuum advance.

I'm holding a wire with a vacuum end that's half black and half grey?

[Donut]

OK, I'll give it a shot.

Pull the spacer and the thin gasket, keep the 3/16's.  Eliminate that from the equation, potential for a vacuum leak.  IIRC the thicker gasket goes with the q-jet, I tried 3 different ones before I got the right one. 
You may have a vacuum leak, but it very well could be internal.

12 deg initial isn't too much, I ran that on mine ('73), more than that and the starter would start to backlash.
The '73 also didn't like  that low of an idle that your shooting for.  I think it was like 900 in park, 700 or so in drive.  Don't try to tune for what a magazine told you, tune for what your truck likes.

[TexasRed]

LOL. I don't actually read magazines. Most of that crud is for high rpm running, not what I can do with a 2.73 rear end, stock tires and 700r4. The fact that it doesn't want to idle lower, is a concern to me, I can raise it to smooth it out, but it appears to me to be a vacuum leak and can mess up proper metering.

I don't have the thin gasket, I've got a manifold, 3/16th gasket, spacer, 3/16 gasket, quadrajet.

[Grim 82]

Did you check play in the throttle shaft? I've installed bushings in two q-jets that had similar symptoms to what you describe and that solved the problem.

Most people run about 12 degrees of initial?

I'm holding a wire with a vacuum end that's half black and half grey?

Yeah mine runs just fine with 12 degrees initial. Pics of the wire/vacuum line? Is it a plastic tube that is supposed to run to the HVAC reserve can on the firewall perhaps?

[TexasRed]

It didn't seem like it had any play. Nice and tight.

It doesn't go to the black ball of doom. It goes thru the firewall on the passenger side. I believe below where a mess of other wires go, or maybe above??

http://i57.photobucket.com/albums/g207/hippiegohome/P4170096.jpg

[454Man]

Couple???
What kinda cam are you running? Stock, mild...
Do you know the brand and specs to the cam also what compression? If you want it to idle lower here is what some do. Power tune your dizzy springs and such, sure you know how. Then bring down your initial to where you want it to idle and comensate the loss timing degrees with the (limited)vac advance, but use ported vac supply so you get the 12 the engine likes. Its what I'm gonna try to get the lope I want.
Disregard the cam question just reread

[TexasRed]

Hmm. I thought maybe the plastic spacer wasn't allowing the carb to totally seal up, so I got one of those metal adapters from mr gasket that the autoparts store sells. I read that sometimes edelbrock's carb pad doesn't have enough meat to properly seal, that's why they offer their sealing plates. That didn't help. I pulled the fitting out of the manifold behind the carb and put in a plug. That didn't help. That's every place for vacuum except brake booster and PCV. I plugged the PCV and it's not that big of a difference.

If I put my hands over the secondaries and primaries, no change.

So. . . .I guess my quadrajet fun is over. Should I get the 4175 from holley, maybe someone on the board gets a discount or the summit racing carb 600cfm?

[TexasRed]

Update: I got the summit carb. Their QC on the fuel line leaves quite a bit to be desired. I had to use some threadsealant. Seems to be okay now. Seems to idle quite a bit better with manifold vacuum at the distributor. I'll add in a few more degrees before lock out and see how she runs. I'm happy though.