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Re: Need help tuning a Schebler Model-S Carburetor
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Posted by zane on July 16, 1999 at 20:23:25 from (216.128.140.97):
In Reply to: Need help tuning a Schebler Model-S Carburetor posted by Chad Larson on July 16, 1999 at 16:44:22:
I'm not familiar with this particular carb, but, this being an early unit, no doubt it's pretty straightforward, without a lot of gimmicks. If it's a single throat, it probably has two needles on it, high speed (load) and slow idle. All any carb does is mix fuel and air. The needles vary the ratio--rich or lean-in fast or slow mode. Chances are the needle closer to the manifold is the idle screw, it's opening into the venturi is downstream from the throttle valve. I assume, from your statement, that you have the engine running. With the engine warm and the choke valve fully open, adjust the idle screw to get satisfactory operation with the throttle "closed". Then rev the engine to about 1/3 throttle and hold it there while you open the load screw until it runs smoothly. You want the screw as closed as possible without making the engine hesitate or "stumble" when you "gun" the engine from idle. You may want to drive the truck a little to make sure it will accelerate normally. The load screw too open will give a rich mixture, cause flooding (usually with black smoke out the tailpipe), and waste fuel. If, after the above procedure, the engine still does not run properly, the carb has plugged passageways, a bad float/bowl system, or you have ignition problems. Make sure the spark advance/retard (manual or automatic) is working properly.
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