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Old 06-05-2011, 07:25 AM
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new engine falls on it's nose

Recently purchased a new GMPP 350 carburated engine for my chevelle and am experiencing a big hesitation on accelerating. From a dead stop pulling away from stop it seems to fall on it's nose for for a second then recovers but this is very annoying and frustrating. It's probably something simple but I'm no great mechanic especially if it's involved with the carb (new holly that came on engine). can anyone suggest suggest the problem area I should focus on....This engine was a totally complete GMPP crate engine and I haven't twinked it since installing in car.

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Old 06-05-2011, 08:04 AM
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I'd start simple, especially with a new running motor. Do a full sweep of your ignition system. Make sure all plugs are gapped properly, connections are good from battery to ignition, plug wires are snapped and in correct location and timing is accurate for your setup. If all that checks out then fool with the carb. Hope this helps.
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Old 06-05-2011, 08:29 AM
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Quote:
Originally Posted by spartan74
Recently purchased a new GMPP 350 carburated engine for my chevelle and am experiencing a big hesitation on accelerating. From a dead stop pulling away from stop it seems to fall on it's nose for for a second then recovers but this is very annoying and frustrating. It's probably something simple but I'm no great mechanic especially if it's involved with the carb (new holly that came on engine). can anyone suggest suggest the problem area I should focus on....This engine was a totally complete GMPP crate engine and I haven't twinked it since installing in car.
Might be the accelerator pump circuit. Holley's instructions are on page 6 and 7 HERE.

If the accelerator pump checks out OK, see if adding initial timing will cure the hesitation. Just don't exceed the max total timing in the process of adding initial timing.
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Old 06-05-2011, 08:31 AM
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symptoms as yours are most always the accelerator pump circuit in the carb, you can adj the cam that moves the pump arm, it should have three positions of adjustment,and adj the pump arm so there is no play, a third adjustment will be the size of the squerters,,but those are the least likely cause. I will sugest you get the tuning CD from holley, it will be a huge help to you.
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Old 06-05-2011, 11:54 AM
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X3 on accelerator pump. Gotta tune that puppy!
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Old 06-05-2011, 11:57 AM
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X4 on accelerator pump, and a good tune put on it.



Cole
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Old 06-05-2011, 12:35 PM
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Looks unanamous... Guess I will focus on the accel pump once I can return to work on car...thanks to all for your thoughts...
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