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Old 02-18-2009, 12:42 PM
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Flat spot when accelerating

I have chevy 383 stroker with 650 Vacuum carb. When accelerating there is flat spot/hesitation before acceleration takes place, very irritating. I fitted the carb out of the box without any adjustments.

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Old 02-18-2009, 01:01 PM
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Check for vacuum leaks around the intake manifold & carburetor gasket. My dad's car did this & when I pulled the intake the gasket came apart in several pieces. Also, check all vacuum lines as a hole or one disconnected can cause this too.
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Old 02-18-2009, 01:49 PM
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Check your float level

Check to make sure your getting a full stroke on the accel pump

Most vac secondary carbs can be adjusted to slow the secondary opening. Do this a little at a time till the stumble goes away.
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Old 02-18-2009, 05:19 PM
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Sounds to me like you need a larger pump shot, i.e. squirter nozzle and possible an accelerator pump cam change. Very common on modified engines. I have yet to put a racy motor together that worked with an out-of-the-box carb calibration, they ALL need tuning.
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Old 02-18-2009, 05:44 PM
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Time for timing!

I agree with all said so far!

But also check your timing and note where it is. Advance it about 3-5 degrees at idle and see if that helps ....as long as the hesitation happens at lower RPMs.

Steve
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