Yes, idle speed is initially set by the screw, but it is controlled by the idle stabilizer. If you turn the idle speed screw while the engine is running, the stabilizer will try its damnedest to maintain 900 rpm. If you get too far off, it will start cycling up and down. This is why you need to set both the idle speed and the timing with the stabilizer by-passed. (Put your timing light on the crank with and without the stabilizer in place. You will see the timing jumping around with it on-line. Without it, the mark stays put.) My point is, with the timing advanced to 5BTDC, the stabilizer can not as effectively control the idle speed. It is already advanced 10 degrees from stock. I have seen this over and over. The idle wanders high and drifts. I was failed at my last inspection for this reason. (They check idle speed as well as tailpipe emissions.) I knew my timing was advanced to around 2BTDC. I pulled in the parking lot, loosened the distributor clamp and turned the distributor. The idle settled down and I went back through for a re-test. Only ten minutes later, all passed easily. I checked the timing when I got home and it was set a about 2 or 3 ATDC. The Digijet distributor has a vacuum retard built into it for emission purposes. The retarded timing (5ATDC) causes it to burn hotter and cleaner at idle. As soon as the throttle is cracked, the retard goes away. Total advance is in line with the other engines. All of this is in the Bentley. Jay
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