spark plug gap

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Jul 22, 2007 | 11:40 PM

riverdog

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Joined: Nov 2005

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spark plug gap

I have a 77 400 . Set the gap to.038 and seems to be fine. Is there a better gap? Motor has intake,4 barrel,rv cam and headers.

Jul 23, 2007 | 06:48 AM

firstonraceday

Laughing Gas

Joined: Dec 2000

Posts: 781

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From: East Texas

Factory specs on the spark plug gap are .042 - .046. I have mine gapped at .042 and the engine is stock (no aftermarket cam, intake, carb, etc.). Assuming you're running the Duraspark ignition, you can set the gap within the above range.

Last edited by firstonraceday; Jul 23, 2007 at 06:51 AM.

Jul 23, 2007 | 10:43 AM

riverdog

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Thanks. I have the duraspark ignition . I'll try widening the gap between those specs.

Jul 23, 2007 | 04:03 PM

fmc400

MSEE

Joined: Apr 2004

Posts: 10,386

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From: Austin, TX

Here is your myth buster for the day. Spark plug gap has nothing to do with aftermarket mods other than the coil secondary voltage. For a given voltage, there is a specified gap that the spark has to arc across. If you are running the standard coil, then run the stock gap like firstonraceday says.

Jul 23, 2007 | 10:38 PM

Torque1st

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Joined: Sep 2001

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The spark plug gap limits the voltage applied to many secondary ignition components. A gap that is too wide can cause other components such as wires, coil, rotor, or cap to fail. A wide gap can also require a voltage that is beyond the capability of the coil and switching circuits which will also cause a no- spark condition. Spark gaps increase with time due to wear, use the smallest gap in the manufacturers specified range.