Carb help
Thread Starter
Pro
Joined: Jan 2005
Posts: 539
Likes: 3
From: Twin Cities Minnesota
Carb help
I am amazed, I rebuilt my carb myself and the car started right up. My son (a diehard mopar fan) was helping me tune the carb, it is a stock Rochester on my 76 L48. He said it seems like it has a vacuum leak because we could not get it to idle below 700 and if you put your hands over the top of the carb it doesn't kill the engine. It did slow it down some but not to the point of killing the engine.
I am still trying to figure this stuff out but he asked me (and thats why I am asking you all) about the secondaries, if you look down the body, should the secondaries be pretty level with the base plate or are they on a slight angle when closed. He thought they were not closing completely. I don't see a gap but he thought they should be flat. We did have a vacuum gauge hooked to the port that goes to the air cleaner and it was holding very steady when the car was running. I am still pumped that it started, can't wait to drive her. A couple more things before road ready. Thanks for your help.
I am still trying to figure this stuff out but he asked me (and thats why I am asking you all) about the secondaries, if you look down the body, should the secondaries be pretty level with the base plate or are they on a slight angle when closed. He thought they were not closing completely. I don't see a gap but he thought they should be flat. We did have a vacuum gauge hooked to the port that goes to the air cleaner and it was holding very steady when the car was running. I am still pumped that it started, can't wait to drive her. A couple more things before road ready. Thanks for your help.
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
You can take a can of carb cleaner and spray certain areas of the carb and see if you get an engine reaction (revving up or bogging down). This will tell you if you have a leak. Sometimes the Q-jets develop a vacuum leak on the rod that runs through the bottom throttle body plate. I believe this is the same rod that the throttle linkage is attached to. The bushings can be replaced, but I recommend a shop do that work.
Melting Slicks
Joined: Jun 2001
Posts: 2,340
Likes: 2
From: Moro IL
If you have some carb cleaner available spray it around the base plate and throttle shafts and see if the idle picks up. A lot of these old quadrajets with high miles tend to have vacuum leaks around the throttle shafts. As far as the secondary throttle shafts not being level, that's normal, they should be at a slightly higher angle then the primary throttle plates.
Pat Kunz
Pat Kunz
Heel & Toe
Joined: Mar 2006
Posts: 15
Likes: 0
Is the throttle cable attached? If so, unattach it and see. Mine was idling fast, and I tried to figure it out. The cable broke off, and the idling went back to normal. The cable was kinked through the firewall. The lever point had to be adjusted by 1/4"
S
S
Thread Starter
Pro
Joined: Jan 2005
Posts: 539
Likes: 3
From: Twin Cities Minnesota
Originally Posted by fritz76
I had the same problem and it turned out I was sucking air through the brake booster. Pinch the rubber hose going to the booster and see if the idle changes.
Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
Cupping your hands over the carb is a test for a lean condition, which will cause a high idle. If you have a leak it could cause a lean condition so eliminate that possibility. After that, you may want to richen up with the mixture screws.
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Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Originally Posted by fritz76
I had the same problem and it turned out I was sucking air through the brake booster. Pinch the rubber hose going to the booster and see if the idle changes.
I worked for 2 weeks looking for a leak ... turned out to be the rear seal on the brake booster. Engine would accelerate by 100 rpm when you pressed the brake at idle.
Replaced the booster....ran like new.
Drifting
Joined: Oct 2004
Posts: 1,496
Likes: 1
From: Lafayette Louisiana
Originally Posted by 76project
If the float was off would that also cause a high idle? I did adjust it per the directions.