The idle adjustment screw is all the way out, I can even see open space between the screw and the linkage but my idle is still at around 1200 rpms... Is there another adjustment or something else that preventing the linkage to close more than it closes now?

 

Is this a new issue or something that has just started?

 

Not sure what you mean... wouldn’t a new issue be something that just started?? If you mean does it have anything to do with the gas and air adjustment I was trying to get right I don’t think so.. Lars told me what to do to get that sorted out. After setting the timing and correctly and adjusting the carburetor my 71 is running great. All cylinders firing, got all its power back and runs smooth...

Problem now is it doesn’t seem to want to drop the rpms down after it warms up...

 

lol, sorry my bad, I meant is it a new issue that had just started or something you had been working on.
If you have adjusted your carb as per Lars, is it possibly an issue with the timing? Lars will tell you 90 % of carb issues are to do with timing.

 

is this happening with Vacuum can hooked up? try pulling hose from vacuum advance can and plugging it. could be you have to much timing from Vac advance. otherwise, a Vacuum leak somewhere?

 

I suspect a vacuum leak then... I have a lazy headlight ( driver side ) and if my headlights are up my windshield whippers door won’t open. My headlights close fine but the drivers side only opens a little and I have to help it up the rest of the way...

 

How about on the choke side, is the fast idle cam dropping down once fully warmed?

 

Not sure, I was checking the other side out and did find a screw that seemed kind of stuck and when I tried to turn it with a screwdriver the choke door suddenly closed from being opened a bit....

 

Dave, I have been fighting a high idle on my car for forever it seems like. Problem is there are so many things that can cause it. Throttle plates (both primary and secondary) misaligned, high idle thats out of adjustment, mixture screws, vacuum leak, timing. I am using the process of elimination, sent the carb to Lars and got that squared away, then messed with the distributor especially centrifugal advance, eliminated that as a possibility. Mine at this point has to be vacuum leak but that's a real rat hole on my '77 with all it's emission stuff. Yours might be easier to trouble shoot, I hope it is, good luck.

 

that's the fast idle adjustment screw.
Did you do this on a cold engine which would account for the choke closing?
When the engine is exhibiting the problem is that screw in contact with the choke linkage?

 

With the vac stuff, I would disconnect it at the carb/manifold and plug it. If your idle changes you have a leak. Then test each hose you disconnected with a hand pump vacuum pump with gauge to the hoses you pulled off. The hoses should hold vac, even if you are testing the whole car. Then just keep following the hose that leaks vac until you find the leak source. I found a melted hose behind the cylinder head with a pencil sized hole!

If you look closely at how tight the throttle blades are to the carb bore, (small feeler gauge) it doesn't take a big hole to raise the rpm a little.

OTOH if the idle does not change when you do this, then the problem is the carb, or an internal vacuum leak like the carb gasket or intake manifold gasket. Spraying starting fluid or brake cleaner around the suspected area will find most of those while the engine is running.

Good luck!

Since I have my carb apart I included some pics (Holley 780 4150 #4803)

Primary transfer slot about right, maybe even too large. I think it was close to mid-slot.


Secondary transfer slot almost closed, should be more like the front one, or more equal. Somewhere between a square opening and mid-slot is usually good. This one looks square or on the tight side.


Secondary throttle blade adjustment screw from bottom side


Secondary throttle blade adjustment screw from top side

Long term I want these two transfer slots pretty equal front & rear, and about where the factory specs are. IIRC it is about .030" Since LARS checked your carb out yours are probably adjusted perfectly, but others may not be. If the back one is opened too far, the front mixture screws don't work well, could have off idle bog, etc If the back one is not open enough you can get a bog on secondary. etc.... The back does have an idle circuit and an idle set-screw. It's just on the bottom. It has no factory idle mixture screw back there since it is pre-set. You want pretty even settings so you get pretty even AFR in the different cylinders. Hot or cold cylinders can sometimes be traced to this. It has been a while since I worked on a Q-jet, but IIRC they were vaguely similar.

Basically when you have one side all the way closed, like your primary, you have a too big air leak elsewhere.

 

leigh1322, all good input. I don't want to hijack daveinspain's thread (I have another similar one going that I started today) but I've done pretty much everything you mention. It is quite possible that I missed something or did something wrong so at this point I plan to retrace all the steps. It's highly unlikely my carb is at fault, Lars had his engine running at 675 rpm with it and that is with 30 degrees advance, 15 initial and 15 vacuum. I have 8 initial and about 7 vacuum, much more than that and it's off to the races again.

 

Does any of these make it change?

1) Pull and plug vacuum to carb from the wiper door/headlight system
2) Adjust choke complete off cold to allow the fast idle choke lever to fall
3) Use an unlit propane torch to "sniff" around where a potential vacuum leak may be

If no change then pull the carb and verify the throttle blades are shut as Leigh describes.
Whatever timing or air fuel you are at....the fact is with zero vacuum leaks and completely closed throttle blades, the engine will stall. It has to. No air to pull fuel and the engine stops. So you need to verify if the issue is leak related or throttle blade related.
And you never answered......is this a new issue? Was it fine before? Did the throttle lever tongue rest on the idle speed screw before? If so.....then find out why the throttle blades will not shut and the most likely culprit is the fast idle cam lever.....which has to be down to let it off the cam......usually cause by a maladjusted choke thermostat.
Let us know what you find....

Jebby

 

Like others said, check the choke side for fast idle drop off, and check for vacuum leak.
Do you still have the same carburetor on your car when you bought it?
Does the choke side look the same as your first photo during idle?
Also, in your first photo, the little clip is missing off of the thermostat spring rod.

 

Deleting this to avoid overlap with my thread, sorry for the confusion

 

I'm only replying to David's '71 high idle problem.

 

Kinda speaking to both as it is almost the same issue......same checks apply. No, there is no secondary air system short of the idle air bleeds. Idle system is typical throttle plate/transfer slot setup.
If Lars had it idling on his engine and you made zero changes to the carb then it is likely not the carb. You are introducing air in from somewhere else......BUT, make sure this level in the red circle is pushed down:



Jebby

 

Possibly wrong gasket under the carb...or gasket inverted or rotated improperly. This might provide an opening for air to get sucked into the intake directly from the outside. It wouldn't take much of an air leak to cause your problem.