TriodeLuvr
Member
My SBC 350 started idling a little rough a week ago. The problem suddenly got worse several days later while I was driving the car. The idle speed also dropped to the point where the motor would almost stall, even in neutral. When stopped in drive, I had to feather the throttle to keep her running.
I've decided to pull the carb (Edelbrock 1406) and spray out the passages. However, I rebuilt this carb a few months back (also new rotor, cap, wires and plugs) and she's been running fine until now. For that reason, even though the symptoms point to the carb, maybe someone can tell me whether other problems can do something similar.
Here's what I have so far...
Full throttle acceleration doesn't seem to be affected. In the transition from idle to midrange under load, the motor seems to suddenly "turn on," as though a misfiring cylinder or three has come to life. The idle exhaust look clean and doesn't smell excessively rich. All the plugs look about the same from one to the next, but the insulation isn't evenly colored. Each one is light tan on one side and white on the other. I haven't seen this before, but most of my work has been BBCs and motorcycles.
The reason I think this is the carb is that the right idle screw has almost no effect. I can't hear any difference, even if I pull it out. The left idle screw operates normally; it peaks the idle speed in about the right location, and the motor dies if I screw it all the way in or take it out. If I spray carb cleaner into the left venture at idle, the motor slows and sometimes stalls. If I spray it into the right venturi (where the idle screw isn't working), the motor speeds up and (I think) smooths out a little.
So, is this almost certain to be the carb, or can something else create symptoms like these? I was thinking about internal issues that might somehow dilute the charge going into one or more right-side cylinders. Is that possible?
Jack
I've decided to pull the carb (Edelbrock 1406) and spray out the passages. However, I rebuilt this carb a few months back (also new rotor, cap, wires and plugs) and she's been running fine until now. For that reason, even though the symptoms point to the carb, maybe someone can tell me whether other problems can do something similar.
Here's what I have so far...
Full throttle acceleration doesn't seem to be affected. In the transition from idle to midrange under load, the motor seems to suddenly "turn on," as though a misfiring cylinder or three has come to life. The idle exhaust look clean and doesn't smell excessively rich. All the plugs look about the same from one to the next, but the insulation isn't evenly colored. Each one is light tan on one side and white on the other. I haven't seen this before, but most of my work has been BBCs and motorcycles.
The reason I think this is the carb is that the right idle screw has almost no effect. I can't hear any difference, even if I pull it out. The left idle screw operates normally; it peaks the idle speed in about the right location, and the motor dies if I screw it all the way in or take it out. If I spray carb cleaner into the left venture at idle, the motor slows and sometimes stalls. If I spray it into the right venturi (where the idle screw isn't working), the motor speeds up and (I think) smooths out a little.
So, is this almost certain to be the carb, or can something else create symptoms like these? I was thinking about internal issues that might somehow dilute the charge going into one or more right-side cylinders. Is that possible?
Jack