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Old 01-12-2011, 11:30 AM
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Shudder, hesitation while driving

Hello all
I have a problem, I drive a 65 impala - 454 , single plane with a demon carb, unk motor mods , 4 speed , 373 gears, duel pipes. A new MSD system, AL box, ignition, distributor, plugs (set to 45) and 8.2 mm wires
I have recently tuned my car, adjusted the timing Ė 12 deg , vacuum- 10, changed PCV to a low flow, and set idle to 800, the carb has been adjusted to operate correctly , I.E secondaryís, and air bleed, I have also changed the power valve to a 4.5 vice a 6
The problem I have is when I drive under normal conditions, in any gear, I experience slight hesitation or shuddering, I noticed this prior to the tuning and changing of the PV but it is more pronounced now. You canít hear difference from the exhaust but can fell it Itís similar to removing your foot from the peddle when driving down hill, you feel the car slow down or sputter.

I have looked at the symptoms of a lean carb but I donít think that the problem.
May be jet sizes.

Any thoughts.

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Old 01-12-2011, 04:21 PM
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I would guess it has something to do with timing. But also, 45 is too much gap for the plugs. If i remember correctly they work best around 25-32.
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Old 01-13-2011, 02:39 PM
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Shudder, hesitation while driving

Hello

your right wrt the spark cap stock plugs come with a 32 or 35 cap however with a MSD system you will not get the best spark at that close a cap, it was suggested that a bigger cap would maximuize the spark system, also wrt plugs, i presently went to a split tip and it was also suggested that a solid core would be best I.E a AC delco stock GMb plug.

Thoughts
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Old 01-13-2011, 02:57 PM
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Float level is correct?

Sounds like a lean missfire. Try stepping up the jets by 2 numbers at each primary and see what it does.
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