61reoldsman

As a side note , I did have issues with the base gaskets that came supplied with my carb that was purchased as a factory issued rebuilt model from Johnson's Speed Shop in Lansing. I had similar issues to you with idling high with ongoing carb adjustments to try and remedy the problem. I even purchased an Inline Tube factory correct piece which after install and use was even worse. So I eventually used 2 thin base gaskets and a thick one in between with light silicone bonding to the intake base .Seems to have worked for me , it'll idle at 800 rpm all day after warm up. Also make sure your tightening the bolts that hold the carb down evenly back to front , side to side. Now I must mention that one of my problems may have been a slightly warped carb base but this method solved my high idling issue , sealed a constant vacuum leak and I was able to readjust my timing back to spec.

defiant1

61reoldsman

Thanks for the advice. I have put the carb on the back burner since I discovered my water pump is junk while trying to tune the carb. And I am redoing the gaskets/RTV on the intake manifold as well, to eliminate any "you have a vacuum leak" talk.

Still waiting to see if CarbDoctor has a fix for his carb. It has been radio silence so far. His basic response is that this has never happened before and that I could adjust the choke pull off (but he doesn't tell me what type of adjustment I need to make).

More to follow...

d1

Fun71

Why the back burner for this? Your local auto parts store should be able to get you a water pump overnight, if they don't have it on the shelf already.

defiant1

I got a different water pump this time as the local auto parts one went **** up after 2 summers, no bueno. Plus R&R takes a bit of time as there is an aftermarket A/C system/bracket that covers the water pump area. Not a quick job at all. And I will paint the water pump and clean everything and paint the parts that need it since I have everything disassembled.

d1

455man

I think the choke pulloff is supposed to open the choke about 1/4".

DocOldsW30

I tend to agree here...Quads like straight linkages. Messed with my 72 Holiday Coupe. 350. Tweaked choke linkage, problem solved.

defiant1

Would you happen to have a picture referencing the linkage and location where it needed to be adjusted?

d1

RROLDSX

I'm no expert on this but is it possible this later model carb required an idle stop solenoid and therefor needs to have the throttle linkage engaged somewhat to make up for the missing solenoid?

Just throwing it out there...

droldsmorland

Have you pulled the black plastic cover off the choke to see if the bi-metal spring is between the forks on the actuator?

Fun71

Good thought, but I don't think all chokes have a fork on the actuator for the end of the spring to connect to it (See image below). Now if the bent end of the spring isn't on the correct side of the actuator then there could be some erratic (or loss of) functionality.

billmerbach

When you start it up if those holes in the top are in fact the problem when you put your finger on them should it increase rpm......any thought more knowledgeable folks?

DocOldsW30

I do know that if things get gummed up inside, it's not good. I'd throw it in the sonic parts washer if you have access to one?

defiant1

[QUOTE=Fun71;687738]Good thought, but I don't think all chokes have a fork on the actuator for the end of the spring to connect to it (See image below). Now if the bent end of the spring isn't on the correct side of the actuator then there could be some erratic (or loss of) functionality.

The spring is contacting/engaging the lever correctly. The electric choke works like it should.

Can you elaborate? I am not sure which holes you are referring to...

In my case, this carb is, for all intents and purposes, brand new. Not a spec of dust in it or on it when I installed it.

d1

DocOldsW30

I'd check for seal leaks then. Sounds like the motor is a bit tired. I've just found a hairline crack on my OEM aluminum W30 intake;( Not a pretty sight but nothing my good aluminum tig welder can't handle

Doc

billmerbach

You said there were some holes in the choke plate right...did I misread something

DocOldsW30

If the little boot-shaped air pipe is missing from the plate, there's your answer. Mine had to be replaced on my 72's Quadrajet.

droldsmorland

Can you take a vacuum reading when the engine is warm and running "normally" off an intake port and post what that is at ~700-750 rpm in park.
Secondly you say the choke is working normally. That means when you hit the accelerator on a cold engine the choke plate closes on the air horn (this should also set the fast idle cam position) What happens when you start and run the engine? Does the plate pull open about 1/8 inch (pull off is working)? Then as the bi-metal warms up does the choke plate begin to open?

defiant1

The holes are in the throttle blades, not the choke plate.

I am not sure what this... I will have to look to see what I can find.

Engine currently in process of having water pump and intake manifold gaskets replaced. So, the vacuum readings will have to wait.
Yes, choke plate and fast idle cam set up correctly after pushing the throttle one time. As electric choke spring gets warmer the choke plate opens all the way. But as I have indicated there is no "fast" idle, if I can get 800 rpm out of it I am lucky...

d1

droldsmorland

I wish I could get my hands on this carb in order to see whats going on. So when its cold and you depress the accelerator linkage the choke plate closes...as that occures the fast idle cam should contact the set screw on the high idle step which you say it does. This brings me back to the vacuum question. When the above scenario occures and the engine wont "fast idle" you have to open the throttle beyond the fast idle cam and set screw to obtain the desired fast idle...right? If so you have either a vacuum leak, or the wrong carb for the application. I think your experiencing a problem in the bypass air circuit. The vac reading will be a good indicator of this. Lets see what happens when you get it running again. The holes in the throttle plates concerns me. The holes are not meant for a pre smog car. You have Cliffs Ruggles book right? If so look at page 28-29 as it has an indepth explaination of what Im talking about. Anyone who owns a Q-Jet needs Cliff and Doug Roes Q-Jet books on their shelves.

Octania

"Anyone who owns a Q-Jet needs Cliff and Doug Roes Q-Jet books on their shelves."

AGREED.
Much is revealed.
Everyone should START by reading the factory CSM [manual] sections which explain the various circuits and linkages, and how they are supposed to work. It's not that difficult, and in an evening you can cover it pretty well. If you have a clean dry carb on hand to play with while going over the text, that's a bonus. See it in real life.

BlackGold

WORD. Knowledge is power. Start with the Chassis Service Manual, then read Roe's and/or Ruggles' books.

MDchanic

Okay, I'll sound like a broken record:

What those guys said.

Also, the Rochester QuadraJet Manual (there's a PDF of it somewhere - I don't have the link here at work), which is essentially the same as what's in the CSM, but with maybe a bit more detail.

- Eric

oldsbucket

You know i do not see a picture of the choke setting screw. how about a picture of the screw you are turning to adjust this, just to be clear that we are all talking about the same

defiant1

See attached pictures, as requested...

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DocOldsW30

[QUOTE=defiant1;688093]The holes are in the throttle blades, not the choke plate.



I am not sure what this... I will have to look to see what I can find.


Stay tuned for a pic from my '72 all original setup...
Doc

oldsbucket

I'll take a look at my 72 . In picture 4 the choke is not activated when it is does the notched cam contact the throttle arm?

defiant1

Yes, the cam rests on the highest notch in the fast idle cam guide when I depress throttle one time. That has never been an issue as the choke works correctly.

d1

oldsbucket

So when it was together did you check the float level? the simplest would be to try another carb temporarily to narrow down the problems

Just got back from taking a look at mine. your curb idle screw is in noticeably further making me more curious about the float operation and vacuum numbers. looks like the throttle plates need to be opened further than normal to support an idle, a low float level could cause this or low vacuum have you taken the top off to look at the needle valve and float settting? move the float up and down to verify smooth operation with the valve, blow out the passages its possible something is stuck.

never had a problem like you describe so I'm just starting from zero here and like i said another known working carb would at lest tell you where to look

DocOldsW30

Ditto,
Doc

defiant1

Figured I would give a status update on this fast idle situation for those who have been giving me advice up to this point.

- I finished replacing the water pump (it went **** up) and the intake manifold gasket as well (let the rtv set up for 24 hours).
- Tightened all the fasteners on the carburetor
- Set idle mixtures screws both at 3 turns out from seated
- Adjusted choke pull off slightly to .200
- I hooked up all vacuum lines like normal and fired up the car
- It was acting like it always did until I advanced the timing and the RPM jumped to 1200 rpm
- I adjusted the timing until I was pulling max vacuum at idle (off fast idle at this point). Max vacuum was 13 at 700 rpm (in park). FYI: the camshaft specs are 217/224 @ .050" Erson custom grind

I shut it down at this point to check for coolant leaks and I haven't set the overall timing yet or put a timing light on it for that matter.

It looks promising so far, one thing I notice was the choke flap did not open fully when I took it off fast idle like it did before when it was running worse... So that is annoying... but I think I am gaining...

d1

Fun71

Interesting. I have an UltraDyne 217/221 cam in my 350 and I get 16" vacuum at idle. I should note that I set my HEI up with 18º initial advance (used to have 10º initial/24º mechanical with Moroso HEI advance curve kit) specifically to get higher idle vacuum.

defiant1

Good to know. I will throw a timing light on it tonight and see where I am at. What rpm did you set the 18* initial advance?

d1

Fun71

I "checked" the initial at 1100 RPM.

I found my notes and discovered my memory wasn't quite accurate. Below are the notes from when I did this; also note that the vacuum advance was connected to the ported nipple on the carb at that time. I haven't checked the idle vacuum now that I have the advance connected to a manifold source.

Reset total to 38 degrees, Initial at 22 degrees
One light and one medium spring - total in at 1800 RPM
Two medium springs - total in at 2200 RPM
Vacuum advance connected
Idle set to 800 RPM in Neutral, 650 RPM in Drive
Vacuum = 16 in Hg @ 800 RPM; 18 in Hg @ 1400 RPM