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Old 04-25-2007, 04:51 PM
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Excessively fast idle

Just put my SBC together after having it apart checking for oil leaks and upon starting it up it came up with a really fast idle(about 2000 RPM). I had the carburetor apart putting on new gaskets and didn't notice anything funny.
I have checked the linkage(its free) and the throttle plates close all the way.
Even with the fast idle it really accelerates good(no hesitation).
What do you guys think? Vacuum leak? Carburetor cracked internally? It does seem to be running rich.
Thanks - Jerry

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Old 04-25-2007, 05:03 PM
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Sounds to me like you need to adjust your carburetor.
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Old 04-25-2007, 05:36 PM
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it sounds like you have to adjust the choke,if the choke isnt opening all way,the fast idle wont come off,let me know how you make out,also what kind of carb.
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Old 04-25-2007, 09:45 PM
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Excessively fast idle

The throtle plates are completely closed, the idle screw is backed out and their is no choke on the carburetor. The carburetor is a Holley 600 CFM 4 barrel 1850-2 with vacuum secondaries.
Jerry
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Old 04-25-2007, 10:31 PM
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The engine needs air and fuel to idle fast, your getting too much of both
from somewhere. The throttle blades are closed so something else is
leaking air, it could be a leaking intake manifold gasket, throttle bushing,
bad vacuum hose. Find the source fix it and half the problems gone.
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Old 04-26-2007, 07:20 AM
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Quote:
Originally Posted by fred56
Just put my SBC together after having it apart checking for oil leaks and upon starting it up it came up with a really fast idle(about 2000 RPM). I had the carburetor apart putting on new gaskets and didn't notice anything funny.
I have checked the linkage(its free) and the throttle plates close all the way.
Even with the fast idle it really accelerates good(no hesitation).
What do you guys think? Vacuum leak? Carburetor cracked internally? It does seem to be running rich.
Thanks - Jerry
where the timing set at? a lot of timing can do the same thing. i can do the same thing on my inline if i want to... also, from the sound of it, it seems as though the cam may be quite advaced also., reason being, with a cam that is advanced, u can put a ton of timing in it and cant hardly get it to ping (i could put over 25* of ign timing in and it wont ping) and the reverse for retarding the cam..
if anything, make sure its not fuel delivery related 1st ( like maybe a bit of trash), then start digging around with the timing to get the idle straightened out. gl
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