Spark plugs and spark plug wirew

The coil failure makes me think the spark plug voltage on my 4.3L GMC is too high.

I did replace plugs and wire after OEM plugs went bad around 30K miles and ECM had a code showing intermittent spark too.

So my question is what brand and what plug type(plug number) can I buy to reduce coil voltage on my 4.3L GMC ?

Would reducing the plug gap reduce the coil voltage??

And what type of plug wires will reduce the coil voltage?

BTW my OEM Delco distributor and rotor didn't last very long..

I would go oem

George, an old physicist like you surely knows that spark voltage is determined by plug gap. Reduce the plug gap to minimum and that's about the best you can do. If indeed the coils were blown by excessive voltage, I suspect old, eroded plugs were to blame.

Although different coils are capable of different voltages a high tension coil will only produce the voltage it must develop to get to ground be it across the plug gap, or past the insulation to some other ground. Thats why one should never crank an engine with the plug wires disconnected, be it a car engine or a lawn mower as the coil can destroy itself building voltage trying to get to ground, some rather quickly, Honda small engines are particularly bad about that. Some magneto actually have a internal protection that allows too high a voltage to arc to ground. To answer your question yes, reducing plug gap reduces the voltage required but you have other issues or bad coils.

What is OEM?
Delco has different plugs

They must recommend something for that application

Mark,
old physicist I resemble that remark.
I noticed some Delco plugs for my truck have .060 and.040 gaps..
I hope I can find the OEM plugs I removed from the truck.
I'm beginning to think my problem may be plug related causing too high coil voltage.
Also noticed some plugs may have a half inch built in gap.

The kids at the auto parts counter know very little except what is on the computer.

Also think the plug wires may play a part with higher than normal coil voltage..

I'm convinced that dielectric breakdown is my problem with the distributor and rotor..

Dielectric breakdown is the formation of conducting paths through an insulating material in the presence of an extremely strong electric field.

It seems really strange to me that you're having problems with the oem distributor caps and coils. They're usually pretty much bulletproof.

Yes a closer plug gap would help. I think I would add a couple extra ground wires to the engine as well. Anything to get the spark to ground faster should help.

George, remember when GM's HEI ignition came out? Spark plug gaps went from around .35 to .60. It wasn't too long, though, that GM lowered recommended plug gaps to more reasonable values, and I've always assumed they determined those huge gaps had some downsides, particularly with ignition component life.

George, I'm sure you already know what I best recall from EE school and years of experience, but hey its been years NO WARRANTY:


The coil ONLY ramps up to a high enough voltage such that current arc jumps the plug gap and the energy (Volts x Amps x Time) is
dissipated .

The voltage necessary for current to arc jump the plug gap is a function of A) The Plug gap B) The medium (fuel compression etc) in which
the arc occurs

The wider the plug gap the higher the coil voltage, so to reduce that LOWER THE PLUG GAP


Your questions:

So my question is what brand and what plug type(plug number) can I buy to reduce coil voltage on my 4.3L GMC ?

I don't see the brand as a major factor in reducing coil voltage..but Im no plug expert nor do I have any specs

And what type of plug wires will reduce the coil voltage?

I don't envision types of plug wires reducing coil voltage significantly HOWEVER types such as pure copper or carbon core or resistive or other suppressor wires can absorb some of the spark energy in the form of heat losses (I Squared R) versus more of it across the plug gap when it fires.

Would reducing the plug gap reduce the coil voltage??

YES

There ya go George this is ONLY my best recollection it may be right it may be wrong, hope it helps

Best wishes

John T

Oem conventional 19354418

ACDelco

Conventional Spark Plug

Part No. R44LTSM
-------------------------------------------------------------------------
OEM double platinum 19299585

ACDelco

Iridium Spark Plug

Part No.
41-162


ACDelco

Double Platinum Spark Plug

Part No.
41-962

All .060 when I gap plugs my gauge goes from .055 to .060 that's my go no go gauge anywhere in-between its good to go. I would not fudge with changing the plug gap. Yes I have had drivability issues using the wrong gap. Fords are the worst for this BTDT and got the wrong info from the under hood label. Look at the latest manufacture information. GM is .060

My dealer has the best price check them out.

Lets muddy the water a little more this is directly from the Manufactory.

Conventional
4.3 Liter V 6 Cylinder(s) 4.00" Bore 3.48" Stroke * GAP .060

Conventional
4.8 Liter V 8 Cylinder(s) 3.78" Bore 3.27" Stroke * Gap .040
6.0 Liter V 8 Cylinder(s) 4.00" Bore 3.62" Stroke * Gap .040
5.3 Liter V 8 Cylinder(s) 3.78" Bore 3.62" Stroke * Gap .040

I advise you to take the Vin. Number to the dealer and ask them its on their parts look up.











This post was edited by Hobo,NC on 03/24/2022 at 06:00 am.

Thanks HoBo

Read again I have edited 3 times. Go to the dealer parts department : )

(quoted from post at 09:02:08 03/24/22)
Read again I have edited 3 times. Go to the dealer parts department : )

Click to expand...

obo, I personally doubt that reducing the coil output is the answer here, but if Geo really wants to try the results of reducing output, we all have experienced/recognized that too large of a ballast resistor in those N tractors will result in such a weak spark that they won't run, so maybe try adding some resistance in primary circuit to reduce coil current. Yes, I know, certain voltage to jump the gap.

The ignition system on your truck is of a pretty rock solid design.

Stick with stock parts and gaps, nothing magical required.

The majority of the problems they encounter will be traced back to a worn distributor gear.

Being that you said you only got 30 000 out of a cap and rotor is a good reason to check and or replace the distributor.

They are inexpensive and you can buy a complete drop in distributor for about the same price as a gear.

"Ohm" the high-tension wires, starting with the coil wire.

Just because they have been replaced a while ago doesn't rule out a "bad" wire or two.

Or, better yet, replace them with a high-quality set of spiral wound/magnetic core wires.

You always brag about how you keep your vehicles inside, is the building you store the truck in DRY and well-ventilated, those 4.3 ignition systems are particularly sensitive to moisture.

And, as the other poster said, have the timing offset checked and corrected to zero.

The more it's off the farther the sparks have to "jump" from the tip of the rotor to the individual high-tension towers.

Sparks create ozone, which combined with moisture tears up the aluminum terminals inside the cap creating a white oxide that gets spun around the inside of the cap, eventually combined with any moisture causing a breakdown of the cap insulation that causes a misfire or shorts the spark out altogether.

If you dig around on GOOGLE you'll find that ventilation of the distributor has been an issue over the years, and changed over time by the OEM or "modded" by owners.

"4.3 Vortec distributor ventilation"

I remember when HEI systems came out they would sometimes burn thru the rotor button. The cause usually was
one or more bad plug wire(s): too much resistance, so spark went the path of least resistance, burnt thru the
rotor button and grounded to the distributer shaft, and caused the engine to die. Mark.

(quoted from post at 10:30:02 03/24/22) I remember when HEI systems came out they would sometimes burn thru the rotor button. The cause usually was
one or more bad plug wire(s): too much resistance, so spark went the path of least resistance, burnt thru the
rotor button and grounded to the distributer shaft, and caused the engine to die. Mark.

Click to expand...

Yep, and the survivors are still doing that today, including ones like George's.

I suspect George's coil and cap failures may be due to a "bad" wire(s) or the timing offset being high.

What should I do with the ventilation?
There is a screen in the bottom of the distributor.
I do store my truck inside a garage or pole barn to prevent
thieves from getting to my tools.

Last two times I lost spark, I had driven to town 3 miles.
Turned the engine off and then it wouldn't start. No warning.
One time I got about 2 miles from home and while driving 45 mph,
it was as if someone turned the key off, the engine died.
The cylinders were full of gas. I thought the engine blew up.
The engine was locked up. I sent it to a mechanic a mile away.
He removed spark plugs and blew the gas out of cylinders..

Do you have a link to the distributor ventilation??