This is in regard to a 2000 Chevrolet Silverado 1500 with the 4.8L engine. The emissions label specifies a spark plug gap of .060, which seems kind of high, although the used spark plugs of unknown age and mileage have a much bigger gap than what is specified. They are Autolite AP5245. I decided …

Sounds about right to me and many plugs do not come pre-gapped in spite of the tales. The ones in my Fords call for .054 and every plug I’ve purchased over the past 20 years has been right around .045 or so. They can be adjusted. The trick is to not get ham-handed with them. And for what it’s wor…

GM reduced the spark plug gap specification when they switched from platinum to iridium tips; https://testing-public.carmd.com/Tsb/Download/42572/2176126 The original spec was .060", the revised gap is .040". All of the spark plug listed for this truck in the Rock Auto catalog have a spark plug g…

As a shop we always replace spark plugs with the same brand and spec that the car came with, or whatever spark plug has been updated to fit your engine. For example the original Delco spark plugs that came in your truck have been superseded to a new number and are now iridium instead of platinum (if…

Interestingly, my gap adjustment tool only goes up to .050, so it sounds like I can adjust these plugs to that, and it should be close enough. Also, I noticed that the ignition wires are all original with a 1999 date code on them, and some of them have rust on the metal spring. So even though the …

I would check with the Chevy dealer to see what plugs and gap are recommended for your engine. I have see cars or trucks that have changed the plug and/or gap after it is a few years old because of in service problems that showed up.

The spring is part of the heat shield, you reuse those when replacing the wires.

[image] tcmichnorth: Mostly nowadays plugs come pregapped. Plugs have been pre-gaped for over 30 years. And from my experience about 20 percent are not gaped properly. Doesn’t matter the manufacturer. You can cap plugs (even iridium), but you have to be extremely careful. You don’t shove a f…

I would think they originally came with AC/delco plugs. Myself I would get the AC/Delco Iridium plug for this if they have one otherwise the platinum version .All the plugs for the 4.8 look to be a .040 gap . AC/Delco double platinums are $4.73 a piece on rockauto .

[image] vipergg: I would think they originally came with AC/delco plugs. GM has been using NGK plugs for a few years now in some of their vehicles (mainly trucks). I have no idea what the OEM plug manufacturer is for this truck/year. But if it is AC/Delco, then I agree - stick with AC/Delco.

Pregapped does not mean they all are gapped correctly. I’m sure it’s a mechanical process, and there is variability in that process. Having outliers means that the process isn’t completely in control. That’s a common issue, and may or may not be controllable, depending on the equipment.

Do you adjust the spark gap on fine-wire spark plugs?

Maintenance/Repairs

bcohen2010 April 13, 2020, 1:51am 19

Thank you all for your assistance with this matter. I ended up adjusting the plugs to a .050 gap. I have not run the truck in all this time due to the amount of work being done to it, and the fact that I needed to order more parts online. Once everything is put back together I will let you know how well it runs.

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Do you adjust the spark gap on fine-wire spark plugs?

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