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Old 07-10-2009, 12:31 PM
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Default Adjusting the Idle and Air/Fuel on my Carb

I finally got my 67' Camaro running but it's idle is really rough. I'm not sure how to adjust the air/fuel ratio screws and idle speed screw on the carb. I actually drove the car a few times around the block to see how it ran. It starts up just fine, but when I put it in gear it stalls unless I have the space to slam on the gas then it will drive until I have to stop. It then just repeats the same problem. I bought a vacuum gage, tac, and a timing light (if it's a timing issue) but I'm not sure where to go from here. A few people mentioned checking the ERG valve. I'm not sure if I have all the ports on the carb plugged/not plugged right? Or if I have the vacuum advance hose connected to the correct port.

The Camaro is a 67' with 327. Edlebrock Carb/Manifold.
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Old 07-10-2009, 02:33 PM
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A picture sure would help to show if your vacuum hookups are right.
Look for any open vacuum fittings on the carb or manifold. If you have any open, plug them.
On an unmodified distributor, vacuum advance wants to be hooked up to ported vacuum (above the throttle plates) on the carb, not manifold vacuum.
First, be sure your ignition timing is set correctly.
Then work on the carb. I usually like to adjust the idle mixture screws using a tuning tach. Other people like to use a vacuum gauge. With the engine running, screw one out until you get your highest rpm reading. Then screw it back in until rpm's start to drop. Finally, screw it back out slowly until rpm's get to where you had your first highest reading. Do the same for the other idle screw.
Make sure your choke is working, and opening up all the way with a hot engine.
After all those adjustments are made, screw the curb idle screw (front left of carb), until you get your desired idle speed. Usually around 800 should be good.
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Old 07-10-2009, 09:41 PM
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Default Adjusting the Idle and Air/Fuel on my Carb

Here are the pictures. You helped me out with the Carb before (throttle connected wrong). Thanks again for all your help with this stuff. It has really helped. BTW—The distributor is an MSD HEI so it's not stock.

Should the middle port in the carb be plugged in the front and back? Should this port be connected to the valve cover? Do I need a PCV valve? I've been trying to figure out how this stuff hooks up to the air cleaner but to no avail.

Also there is a port right behind the carb on the manifold. It has two stems (the port/stem is shaped like the letter F) one stem has a metal tube connected to it and the other right below it has nothing, not even a plug. I thought it was for power brakes but I don't have power brakes.

Where do I find a tuning tac? Can a vacuum gage be used?

Thanks again for all the help. I'm glad there are people out there who are still knowledgeable about this stuff.

Chris
Attached Images
File Type: jpg Carb5.jpg (39.0 KB, 12 views)
File Type: jpg Carb7.jpg (18.3 KB, 9 views)
File Type: jpg Carb6.jpg (6.2 KB, 6 views)
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Old 07-11-2009, 12:34 AM
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I see you have a breather on the passenger side valve cover. That's good, but you also need to vent the drivers side cover with a PCV valve and connect the other end of the hose to one of the large center ports on the base of the carb. Those ports are full manifold vacuum.
I presume you have an automatic trans? That metal tube connected to the fitting on the manifold would go to the vacuum modulator on the trans. You can, and want to plug the other open fitting.
If you don't have a tach that you can use under the hood, use the vacuum gauge. If you do have a tach that will work, you can use both if you want to.
For now, you can connect your vacuum gauge to that manifold fitting to set the idle mixture screws.
With a vacuum gauge, you set the idle screws almost the same way as I described with the tach, just a little differently. You first want to crank in (lean out) one of the idle screws until the engine starts to shudder. Turn the other screw out until the engine gets to max rpm's. Then adjust the first screw out the same way. This procedure tends to leave your idle setting slightly rich, so you'll then want to crank the screws in 1/8-1/4 of a turn. Once you do it once or thrice, you'll be able to "hear" the differences in the engine and where it wants to be to idle the best.
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Old 07-11-2009, 03:45 PM
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Right now I have an Edlebrock air cleaner with a Stem on the bottom but I don't know where that one hooks up to. Should I get an Air cleaner with no hose/stem attachment? Also Is the vacuum advance hose right?

Thanks
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Old 07-12-2009, 12:59 AM
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If you were to use the fitting at the base of the air cleaner, it would get hooked up to the valve cover vent hole, in place of the breather you now have. Keep what you have and cork off the hole on the cleaner base.
Your vacuum advance is hooked up correctly.
Here's an article about distributor advance: http://www.corvettefever.com/techart...wer/index.html
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Old 07-12-2009, 09:07 AM
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You really should have a mechanic go over the motor. Find a older guy that likes to work on after market setups. You need to be sure everything is hooked right and functioning right before you adjust anything on the carb. Back in the 80's we use to get a least one car a week in that the customer requested "Adjust carb". To us that ment figure out why the car was not running right and put the carb adjustment back where the factory set them cause someone was playing with them. The only time you should adjust the carb is 1.) When you are installing a new or rebuilt carb on a motor and you are 99% sure there is no other issues. 2.) When your car is hooked to a four gas analyzer and adjusted for emissions 3.) (The best way) When its on a dyno

Your not sure if the hoses are right, Your not sure the timing it right, Is the carb new? how do you know if its gunked up from sitting? You should never try to adjust a carb in that situation. On a saftey note you really need to get that return spring off the hose clamp. That hose pops off at WOT and you could be stuck at WOT. That spring really needs a hard mount.
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Old 07-12-2009, 10:50 AM
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Thanks. The picture is actually a before shot of the carb. Who ever worked on the car last had it hooked up incorrectly. I've since corrected the return spring and throttle linkage. The spring is now the dual spring going towards the back of the engine which hooks to a hard bracket that I fastend to the manifold. I also just rebuilt the carb so I need to adjust it. The idle is too high. Also, I'm trying to learn to do this stuff myself because it's something I enjoy doing. I do appreciate the input all the same any advice I get from people who actually know what they are doing is always heeded.
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Old 07-12-2009, 02:03 PM
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Maskedman, it sounds like you're on the right track and getting things situated with your setup. And you've been doing the right thing, asking the right questions before you do something wrong.
If I were you, I wouldn't go chasing off to a mechanic, for several reasons.
1) You sound like someone who is willing and able to learn. Taking it to a mechanic doesn't help to build your knowledge base at all, does it? How many here were "born" knowing how to work on cars....none. Plus, there's nothing more rewarding than being able to diagnose and fix your own problems.
2) These old engines are the easiest things to work on, and they don't require you to have a degree in computer science either.
3) You have a good support system right here, and chances are pretty good that you'll be able to find what you need.
4) If you ever did need a mechanic, you would want to find an old-timer. A lot of new mechanics don't know the "old school" tricks for setting up an old style engine. If they can't hook it up and have a computer tell them what's wrong, they're lost. Working on these old engines sometimes requires the person to be an "independent thinker".
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Old 07-12-2009, 11:27 PM
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Camaro 69,


Let me first start by saying You're the man!

I followed your advice to the letter and got the car going the way it should, runs great. Thanks for all the support. I think the PCV hook up made big a difference as well as the air/fuel/curb idle adjusting. I ended up using the tuning tac and it worked like a charm. As it's apparent that I am far from being an expert, you'll probably be hearing more from me in the future if you don't mind. Learning how to do this is the biggest part of the fun for me, not just the end result. This stage I really just intended to get the car running good enough to get her home, but she runs better than good now.

Now I can start the wonderful, albeit time consuming, task of learning to restore this beauty.

Thanks
Maskedman

Last edited by maskedman; 07-12-2009 at 11:32 PM.
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Old 07-12-2009, 11:27 PM
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327, chevy, curb, gear, highest, idle, ignition, ram, recommended, speed, stalls, timing, tunnel, v8, vacuum

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