fast idle
Thread Starter
Intermediate
Joined: Nov 2005
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fast idle
Ihave a 69 350/300 4 sp.that sometimes does not idle down when Im coming to a light or stop. It will idle down if I hit the gas pedal quickly. Had a guy look at the carb and he said everything looks ok. What other areas should I be checking?
Tech Contributor
Joined: Aug 1999
Posts: 14,373
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From: At my Bar drinking and wrenching in Lafayette Colorado
That's not an uncommon problem on the older Q-Jets. What happens is that the throttle shaft bore in the carb gets a little bit a wear. With the throttle return spring pulling the throttle lever back, and the throttle cable also pulling back, the throttle shaft can "****" slightly in the bore from this offset and not return to a consistent idle. If this is the case, you can solve the problem by attaching the throttle return spring on the TOP of the throttle lever instead of at the bottom, and bring the spring forward to a 90-degree bracket attached to one of the forward manifold bolts. By having the spring pull forward instead of back, the throttle will return to idle without needing to install new shaft bushings in the carb.
Safety Car
Joined: Jun 2002
Posts: 4,135
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my holly 670 street advender has a fast idle set screw so you can tune the idle when the choke is pulled in,,,and the normal idle screw when the choke is open and warmed up,,,i noticed that when i switched to alum heads ,,the idle goes up when i turn the engine off because they cool faster than the iron heads,,,but that can be adjusted using the fast idle set screw
