Carb Adjustment Questions
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Senior User
Joined: Jul 2009
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From: Canyon, TX
Carb Adjustment Questions
I've searched the forum and web, getting lots of good info on the adjustment procedures. But I've got a couple questions I still need help with:
My truck is running poorly at start up. Had some engine work done (OK, it was pulled out and overhauled) and something is off.
Once it warms up it runs fine. But it stutters when I first start up and needs the throttle. I adjusted the fast idle and it does OK now. But I figure I better do the full adjustment with idle mixture screws and get it right.
I have understood that the vaccum gauge goes in the back of the carb. But see the pic: the brake booster isn't hooked up to that port (it goes in the manifold directly), but it looks plugged somehow with a threaded something. Can anyone identify it? Is this where I should hook up the gauge? Maybe the front?
I have an Edelbrock carb, a 1405 600 cfm and the motor is a FE 428. No choke on the carb, either manual or electric. I understand how to use the guage and make the adjustments, just need help with "attachment." Thanks in advance!
My truck is running poorly at start up. Had some engine work done (OK, it was pulled out and overhauled) and something is off.
Once it warms up it runs fine. But it stutters when I first start up and needs the throttle. I adjusted the fast idle and it does OK now. But I figure I better do the full adjustment with idle mixture screws and get it right.
I have understood that the vaccum gauge goes in the back of the carb. But see the pic: the brake booster isn't hooked up to that port (it goes in the manifold directly), but it looks plugged somehow with a threaded something. Can anyone identify it? Is this where I should hook up the gauge? Maybe the front?
I have an Edelbrock carb, a 1405 600 cfm and the motor is a FE 428. No choke on the carb, either manual or electric. I understand how to use the guage and make the adjustments, just need help with "attachment." Thanks in advance!
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
The rear port in your first picture runs to manifold vacuum. You can leave it plugged like you have it; sometimes people will install a barbed hose fitting here to run power brakes.
In your second picture, the small port on the left goes to ported vacuum and the small port on the right goes to manifold vacuum. The left one goes to ported vacuum because it's higher and therefore above the throttle plates. The vacuum gauge gets connected to the small port on the right because a vacuum gauge always connects to manifold vacuum. tinaheels had it backwards.
In your second picture, the small port on the left goes to ported vacuum and the small port on the right goes to manifold vacuum. The left one goes to ported vacuum because it's higher and therefore above the throttle plates. The vacuum gauge gets connected to the small port on the right because a vacuum gauge always connects to manifold vacuum. tinaheels had it backwards.
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Senior User
Joined: Jul 2009
Posts: 377
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From: Canyon, TX
Heh, heh...not a problem. Look, I spelled "vacuum" wrong in my post. 
Well, the best reading I can get is 15, but at least I know I don't have it too rich. I couldn't figure that out without a guage so it was worth getting to set the two screws just at the point when I get the highest vacuum.
Got the fast idle a about right, I think, so it's running at about 800 RPM. Pretty close to where it was before and ran fine. Was somewhere near 300 or so a few days ago--still don't know why it dropped so far.
Thanks again.
Well, the best reading I can get is 15, but at least I know I don't have it too rich. I couldn't figure that out without a guage so it was worth getting to set the two screws just at the point when I get the highest vacuum.
Got the fast idle a about right, I think, so it's running at about 800 RPM. Pretty close to where it was before and ran fine. Was somewhere near 300 or so a few days ago--still don't know why it dropped so far.
Thanks again.
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