Talk me into, or out of, it...

[Scooterwrench]

Cap and rotor, and plug wires, new when I bought the truck a year ago, because they were very bad. The plugs were new, too but sat on my workbench covered in other parts and I somehow forgot about them.

That tach/dwell tool is nice but when I found it, I was actually looking for an analog one like my buddy has. Both are very "old school" by now but at least still usable on the TBI's ignition setup.

Richard

Have you ever seen Shurkeys way of killing cylinders? He shoves finishing nails up into the cap end boots so they're making a connection with the terminal then touches them with a grounded wire to kill the cylinders,pretty clever!
Don't get too crazy tightening the plugs. The valance of the plug is pretty thin and if you put too much mojo on it it can crack the porcelain inside,learned that the hard way. Also you don't need platinum, iridium, plutonium or any other sillyidium plugs if your changing them like your supposed to. I've been running regular 'ol Autolites in everything I own since the mid '90s and the only time I've ever had a problem is when the carb messed up and fouled them. Set your plug gaps to .040" MAX!!! I like .035". Gaps are always going to grow and the wider the gap the more voltage the coil has to build to jump across it which puts more strain on the cap, rotor and wires. Those plugs you install with .044"-.046" is going to grow to .050" in time backing that voltage up even more. Find your plug gauge and use it, never take it for granted they come properly gapped. These things get tossed around and dropped and the gaps get beat to $****. I will not buy plugs online! I go to the parts store and inspect every one before I pay money for it. If you ever drop a plug on a concrete floor go ahead and toss it in the trash can, good chance the porcelain broke inside. The best plug gauge is the wire type and adjust the ground terminal until you can just drag the wire through the gap with a little resistance. Last thing, paint the threads with antisieze, you may want to get it back out some day. This is especially important with aluminum heads with soft threads that will pull if the plug sticks.

 

[Caman96]

You don’t NEED iridium plugs, but there’s no reason not to use them.

• Durability
  Iridium is a hard, silvery-white metal that's stronger than platinum and has a higher melting point than copper. This makes iridium spark plugs more durable and able to handle high engine temperatures, and they can last up to 100,000 miles or more.
  
  
• Ignition
  Iridium's good conductivity and small central electrode create concentrated, strong electrical sparks that help with quick combustion and ignition. This can lead to better engine performance and power.
• Fuel economy
  Iridium spark plugs can improve fuel economy by burning fuel more efficiently and requiring less voltage to create a spark.
  
  
  
• Corrosion resistance
  Iridium spark plugs are less prone to deterioration and sudden failures than other spark plugs.

 

[454cid]

My wires were destroyed by removing them, but they had been there a lot longer than a year. I had a few ends pull right off. They were ACDelco wires, but not the originals.

 

[someotherguy]

Have you ever seen Shurkeys way of killing cylinders? He shoves finishing nails up into the cap end boots so they're making a connection with the terminal then touches them with a grounded wire to kill the cylinders,pretty clever!
Don't get too crazy tightening the plugs. The valance of the plug is pretty thin and if you put too much mojo on it it can crack the porcelain inside,learned that the hard way. Also you don't need platinum, iridium, plutonium or any other sillyidium plugs if your changing them like your supposed to. I've been running regular 'ol Autolites in everything I own since the mid '90s and the only time I've ever had a problem is when the carb messed up and fouled them. Set your plug gaps to .040" MAX!!! I like .035". Gaps are always going to grow and the wider the gap the more voltage the coil has to build to jump across it which puts more strain on the cap, rotor and wires. Those plugs you install with .044"-.046" is going to grow to .050" in time backing that voltage up even more. Find your plug gauge and use it, never take it for granted they come properly gapped. These things get tossed around and dropped and the gaps get beat to $****. I will not buy plugs online! I go to the parts store and inspect every one before I pay money for it. If you ever drop a plug on a concrete floor go ahead and toss it in the trash can, good chance the porcelain broke inside. The best plug gauge is the wire type and adjust the ground terminal until you can just drag the wire through the gap with a little resistance. Last thing, paint the threads with antisieze, you may want to get it back out some day. This is especially important with aluminum heads with soft threads that will pull if the plug sticks.

A lot of good points and in line with what I learned working with my buddy Dennis as a mentor, decades ago. If he saw the counter person slap the box of plugs down (and for some reason they always seem to do it) he'd loose his mind and insist they get thrown in the trash, because that's what they were after that.

BTW, the old CR43TS's that came out didn't really seem to grow in gap.. in fact most were around .035; of course I don't know what they were when they were installed by PO.

So I started today by pulling the wires and checking resistance of each one to see if they were in spec. The generic 12K ohm per foot in mind, all of them checked out - depending on length, anywhere from 9K to just under 14K.

Then I pulled the plugs and it became rapidly clear why it was running so poorly. Some were smashed almost completely closed, less than .020. Only one of them was near normal at .040. Went ahead and ran compression test and got nearly even results on all cylinders, which was reassuring - about 165psi each, though it bled off quickly on every single one - not sure but I think the antique Snap-on gauge set I'm using has a bad seal somewhere.

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Kinda puzzled on these plugs as I don't feel like I went animal tightening them up. Also, I swear they didn't look like this going in; I'd like to say I would have noticed!! But it was a long morning after a long night, is it possible I overlooked these ridiculous gaps? The boxes looked brand new, no evidence at all of mishandling; I even just went and dug them out of the recycling to confirm. Comparing the ACDelco 1 to the CR43TS, they eyeball same length from seat to tip..

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Which brings me to the next issue.. now that I've found my gap gauge, I'm pretty sure you're not supposed to use these disc/coin style tools to gap a platinum plug.. right?

Richard

 

[0xDEADBEEF]

Correct, you need to grab the strap only when gapping those fancy elements. They are hard but brittle.

 

[95burban]

@Scooterwrench, i ran autolites in a nitrous small block. Excellent cheap spark plug.

I know you probably don’t want too, but I suggest removing the fancy plugs and going back with copper ac delco or autolites as suggested above. Have you ohm the plug wires yet?

 

[someotherguy]

@Scooterwrench, i ran autolites in a nitrous small block. Excellent cheap spark plug.

I know you probably don’t want too, but I suggest removing the fancy plugs and going back with copper ac delco or autolites as suggested above.

Considering it but I'm curious on why you are so against them in particular? BTW locally a CR43TS is $5/ea while they're $1.67 at Rock. But, I really want to put the truck back together today so I can get it out of the garage. If I order from somewhere, it'll be next Tuesday at the earliest that I can work on it.

Have you ohm the plug wires yet?

Yep. reply 724 https://www.gmt400.com/threads/talk-me-into-or-out-of-it.60810/page-73#post-1442943

Richard

 

[95burban]

Well, I don’t have any scientific evidence, just personal experience. I believe some of the older ignition systems run better on copper plugs since that’s what they were designed to use. Iridium’s take more energy to fire causing rough or irregular idle.

You also can’t (you can but not suggested, pre gapped for a reason) gap a plug with precious metal on the tip. It will hurt the metal.

I’ve only ran copper plugs on sbc and bbc (street, strip, nitrous, alcohol). In my newer stuff I run iridium just because that’s what it calls for.

We ran copper champions in our natural gas cat and Waukesha engines, switched to iridium to have longer plug life(12 to 16 cylinders, $100 a spark plug) They lasted longer but were more finicky and you could see that by the voltage and secondary voltage screen. Any sort of trash or aluminum from detonation that would get on the tip would cause issues, you would have to replace the plug. We would clean The copper plugs and reuse them if needed. These engines ran 24/7 365 at 100% load at full rpm. Only shut down on a 90day PM schedules.

 

[Road Trip]

You don’t NEED iridium plugs, but there’s no reason not to use them.

• Durability
  Iridium is a hard, silvery-white metal that's stronger than platinum and has a higher melting point than copper. This makes iridium spark plugs more durable and able to handle high engine temperatures, and they can last up to 100,000 miles or more.

This was exactly my default mindset the first time I replaced the plugs in a newly
acquired DD. I was at a brick-and-mortar parts store, fully intending on a set of my
preferred no-nonsense copper V-groove NGKs. And then a set of Iridium plugs also
showed up on the screen on special for nearly the same money? Wow, get jewelry-grade
Iridium plugs for the price of copper? What a deal!

I carefully installed these in 2020, thinking that at my advanced age these should literally last
a lifetime. :0) But not that long ago, I started noticing increasing drivability issues, and pulling
the plugs after 40K miles showed them to be completely toast -- the gaps grew from .044"
installed to ~.088" in the interval? The good news is that I took before photos in 2020, and
after photos in 2024, so no guesswork involved. And after finding the fine print in a remote corner
of the manufacturer's website it all now makes perfect sense: (Why didn't these last as long as I thought they would?)

****

@someotherguy, good on you for taking such an interest in reading your plugs as part of your
troubleshooting/repair effort. SES lights & DTC codes are a good starting place (if they kick) ...but
in reality it is just the ECM/PCM/VCM's considered opinion after running test routines that were written
in order to meet a looming engineering deadline & tightening EPA mandate a quarter-century ago. :0)

Live data is one step closer to the truth, but since everything affects everything else (bad ignition can
feel like a fuel delivery issue, and vice versa, even before you layer on a feedback loop) ...even a savvy
mechanic can still be led down the garden path.

But the closer you can get to the combustion chamber, the more unvarnished truth will be revealed.
And the most truth you can put in your hand is the spark plug that lives in that combustion chamber.

A lot of people like to make it seem that there is a lot of mystery to reading plugs. And if my buddy buys
a 250K mile work truck with plugs that have been in there forever, and he wants me to make a definitive
read? Well, this is one of those times where reading plugs is *still* a bit of a mystery. After they were
bought, did the mechanic installing them accidentally drop 1 or more? How are these exotic plugs
supposed to wear? And how did the PO drive the thing?

But if we replace those 'steeped in mystery' old plugs with a fresh set from a vendor we trust (from previous
firsthand experience) ...*now* we can have a set of plugs that will tell us valuable info. When examining
these plugs after being in service for awhile, we will know how many miles are on them, how the vehicle was
driven, and even how many quarts of oil were consumed by the engine since they were installed. (!)

Pulling *those* plugs after a few thousand miles can give us a wealth of information on both the state of
tune as well as the mechanical health of the engine. I personally gain confidence in my understanding of
what's really going on inside when I can compare what the plugs look like (and the story that they tell)
match the fuel trims that the live data stream is reporting.

So IMHO you are on the right track with the new plugs. Take a before photo or two now, so that we have
something to compare against 3-6 months down the road. (Note: In the case of cylinder #4, we might
get a clue after only a couple of weeks have passed. It's way different than the others.)

****

Anyway, the point I was originally trying to make is that fancy spark plugs sometimes have fancy fine print
that defy commonly held expectations. Buyer beware. :0)

 

[Road Trip]

My wires were destroyed by removing them, but they had been there a lot longer than a year. I had a few ends pull right off. They were ACDelco wires, but not the originals.

I used to have similar ongoing maintenance issues with quality wires that I had spent good money on,
and I hated it when this happened. But once I started using dielectric grease on the inside walls of the spark
plug boots (applied with a Q-tip) the wires would then come off afterwards perfectly with nominal effort, and
thereby outlast the rest of the vehicle. No matter how many times I was in there looking for peppered plugs
or other clues as to the state of tune.

Dielectric grease is one of the greatest inventions by mankind, right up there with grilled food that's eaten
right away while standing up & engaged in tall tales with fellow old truck enthusiasts. :0)