What spark plugs and wires?

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JoeJoe1993

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I have a stock 97 GMC 1500 305 5 speed. I need to change the spark plugs and wires. What would yall recommend going to? Staying the same or changing for updated ones?
 

Schurkey

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If this were me, I'd be looking for the recommended spark plugs...and then buy the version with the shorter side electrode for a somewhat-smaller plug gap.

So if the plugs are "R44LTS6", I'd get R44LTS without the "6". Same plug but intended for a smaller gap.

You can blow more money on Iridium or Platinum plugs. Your choice. I'd still be looking for a .040--.045 gap rather than ~.060 gap. Remember, you can't change the gap on Iridium or Platinum plugs. If the gap isn't right "out of the box", return 'em and get different plug(s) with the correct gap.

I always try to get plug wires that are helically-wound metal wire, rather than "carbon rope" conductors. Both suppress EMR, but the helical wires seem to have a longer service life.

The Summit house-brand universal-fitment wires have been my first choice for years. Available in multiple colors, cut the wires to length so they fit EXACTLY, and then crimp on the distributor ends. Sets include a crimper tool.
Example:
www.summitracing.com/parts/sum-881020

FOLLOW THE ORIGINAL PLUG WIRE ROUTING including replacing the fragile looms that are so often broken/missing.
 
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RichLo

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Remember, you can't change the gap on Iridium or Platinum plugs. If the gap isn't right "out of the box", return 'em and get different plug(s) with the correct gap.

Really? I know you cant run the round slider style gapper on them but I've grabbed onto the ground strap with a small needle nose at the base to adjust them up or down before. Then I used that round slider as a checker. This is not only for GMT400 going up to .060 but for adjusting the gap on small displacement turbo factory engines as well where a small adjustment can actually make a difference with spark blow-out.

I trust your input Schurkey! Have I been doing it wrong?

I know I may be wasting money but if I want to throw plugs in something and not worry about the gap increasing over 75-100k miles, Iridium and Platinum are the only way to go. If I want to adjust gap should I switch to standard plugs and just switch them out every 30k miles instead?
 

RichLo

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Thats why I use the needle nose at the base of the ground strap and not touching the electrodes besides to just check the gap distance.
 

Schurkey

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IF a person has to adjust the gap on fine-wire spark plugs (Platinum, Iridium) then using a tool to grab the side electrode at it's base where it's welded to the shell is the better way. CLOSING the gap is probably less risky than OPENING the gap, especially opening the gap by using a wedge tool.

Cramming a wedge tool between side and center electrode can bend the fine-wire center electrode, and knock the Platinum or Iridium "lump" off the side electrode.

I have heard--but not confirmed--that some Platinum/Iridium plugs don't really have a discrete "Lump" of the precious metal, one or both electrodes are merely "plated" with the Platinum or Iridium, and the plating can be cracked by bending.

I discovered my Iridium plugs for my Trailblazer were counterfeit ACDelco, in part because the gaps were not consistent plug-to-plug. Two out of six were right, the rest were way off. Sent photos to GM, they confirmed the plugs were not "authentic".

I really like Iridium plugs in some engines--feedback port fuel injection, not worn-out oil-burners. The original plugs in the Trailblazer went almost 170K miles, pulled at 90K intending to replace 'em...and they looked so perfect I put anti-seize on the threads and screwed 'em right back in even though I'd already bought the replacements. I'm not saying I'd put Iridiums in a TBI, and absolutely not in an engine fed by a suck-and-hope carburetor.





Even "normal" spark plugs have a "gap range"; the side electrode shouldn't be bent to "whatever" gap is desired. The side electrode is engineered to be at or near a certain gap width, opening or closing the gap beyond that causes the side electrode to not be angled properly in relation to the center electrode. The manufacturer of the plug should have gap recommendations for each plug part number. This is sort-of seen in the plug part numbers (sometimes) where a given base number is followed by a "6" or "8" indicating a recommended gap of .060 or .080; or perhaps with a suffix "X" for "eXtended gap". Wide-gap plugs have longer side electrodes to allow the wide gap.

From ngksparkplugs.com/en/resources/5-things-you-should-know-about-spark-plugs
3. Gapping fine-wire spark plugs
While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap. If the gap must be adjusted, use a tool that only moves the ground electrode and does not pry between or against the electrodes. NGK also recommends adjusting the gap no more than +/- 0.008” from the factory preset gap.
As a guy who just regapped .060 platinum plugs to .045, I would like to know why this is bad in more detail as well.
So with NGK plugs at least, collapsing the gap from .060 to .045 (.015) would be improper. Other manufacturers might have a different recommended gap range.
 
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Erik the Awful

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Back in the day I learned:

Chevy - AC Delco
Ford - Autolite or Motorcraft
Chrysler - Champion
Toyota/Honda/Mazda - NGK or Nippondenso
BMW/Porsche/VW - Bosch

...but...

Champion and Autolite have become absolute garbage. The Champion plugs in my wife's Chrysler 300 ran like butt. The welded-on ground strap on one of the Autolites in my Mustang fell off, causing an immediate misfire and probably a dozen hundred u-shaped stampings on the top of my piston. I put NGKs in both and have had zero issues. NGK is my go-to problem solver for plugs and coils. That said, AC Delco still seems to be making quality spark plugs, and I run them in my Chevys.
 
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