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Old 05-17-2017, 03:33 PM   #1
57Suburb
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Vortec heads, HEI and spark plug gap

I'm noticing that all the IR and Plat plugs recommended for the vortec headed sbc engines come pre-gapped at .060. I've always thought that the base gap for these should be .045 and that's how I've gapped copper plugs in the past. Have I been doing this wrong all this time, or does the coatings on these plugs require a bit more gap?
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Old 05-18-2017, 07:24 AM   #2
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Re: Vortec heads, HEI and spark plug gap

I never pay much attention to what plugs come gapped at I just gap them for my application. With a plug fitting more than one application they all may need something different. Then if you have made changes to the factory configuration like carb, intake, cam, or ignition you may need to adjust from the factory spec a bit to fine tune what works.
Jimmy
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Old 05-18-2017, 08:51 AM   #3
57Suburb
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Re: Vortec heads, HEI and spark plug gap

The Iridium and Platinum plugs all come pregapped to factory OEM specs because you're not supposed to touch them with a gapping tool. Cracks the coating if you do. So can someone confirm that the .060 gap these plugs come at is indeed factory spec for chevy vortec headed engines?
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Old 05-18-2017, 10:52 AM   #4
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Re: Vortec heads, HEI and spark plug gap

I have gaped them many times. Here is what NGK says about gaping there plugs with these types of electrodes.
Jimmy

Do I need to set the gap when installing a new set of plugs?

A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a preselected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy and accelerated plug wear. It is always best to check the gap against the manufacturer's specifications. If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium, be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode.

Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".

If you have any questions, please contact the NGK Spark Plugs Tech Staff:
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Old 05-18-2017, 02:55 PM   #5
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Re: Vortec heads, HEI and spark plug gap

Well, I've done some more digging and came up with the info I believe to be correct. From the GM service manuals;
87-95 5.7L vortec motors - .045 gap
96-00 5.7L vortec motors - .060 gap

The hotter ignition in the later vortecs offered a larger gap potential that enhanced combustion burn creating a bit more HP and fuel efficiency. This info is for stock motors only. All the info provided by PGsigns is valid in determining gap for motors that have been modified. Just leaving this here for people searching info on gaping plugs.
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Old 05-18-2017, 11:29 PM   #6
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Re: Vortec heads, HEI and spark plug gap

To clarify....the '87-'95 5.7 engines are NOT a Vortec engine. They are simply a swirl port TBI engine. Only the '96-'02 L31 engines are 5.7 Vortec engines.
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Old 05-18-2017, 11:37 PM   #7
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Re: Vortec heads, HEI and spark plug gap

Yup, and none of them used an old style in cap HEI. The HEI you have needs at a minimum .045 gap, regardless of what heads you have.

Gary
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