Spark Plugs type for 1980s cars with distributor

[alcyon]

Ok I read this thread today : https://bobistheoilguy.com/forums/t...c-metal-spark-plugs-that-underperform.388156/
So I have similar question.
My car is a mid 1980s car with a turbo engine that uses a distributor and separate ignitor. Its is a 1G Gte engine, but americans are not familiar with it, so think of the Toyota 7M GE engine. Non contact point type distributor ,with electronic timing advance.
I am unsure what type of plug came with the car back in 1988, but I know the heat range required is 6.
Since it is not a coil on plug engine, am I better off with a copper plug and changing it out every 2 years? Will a modern iridium shorten the life of the distributor since it requires higher voltage to create spark ?

 

[Astro14]

Ok I read this thread today : https://bobistheoilguy.com/forums/t...c-metal-spark-plugs-that-underperform.388156/
So I have similar question.
My car is a mid 1980s car with a turbo engine that uses a distributor and separate ignitor. Its is a 1G Gte engine, but americans are not familiar with it, so think of the Toyota 7M GE engine. Non contact point type distributor ,with electronic timing advance.
I am unsure what type of plug came with the car back in 1988, but I know the heat range required is 6.
Since it is not a coil on plug engine, am I better off with a copper plug and changing it out every 2 years? Will a modern iridium shorten the life of the distributor since it requires higher voltage to create spark ?

I’m curious, other than a change in gap, why would the metal with which the electrodes are made change the amount of spark voltage required?

The ionization energy will depend on the cylinder pressure and the size of the gap. That’s basic physics. So, your ignition system, either exceeds that energy, or it doesn’t (in which case he will get no spark).

But as long as the electrodes are similarly conductive, the amount of voltage required to make it work is going to be the same.

A higher voltage will work more effectively, whether the spark plug has steel electrodes, platinum or iridium.

I wouldn’t get too concerned after reading that thread. It’s predicated on a great deal of misinformation.

In general, I tend to stick with the original equipment, manufacturer recommendation, and that includes heat range, electrode material, and replacement interval.

 

[Chris142]

If you had a long run of wire the precious metal may cause an issue. But the amount in a plug is only at the tip, maybe 1 inch long at the most. Wont make any difference on plug wire life,cap etc.

 

[eljefino]

The materials in the spark plug (and the ignition wire) have little to do with the ignition voltage required. The air gap is pretty much all of the "resistance" in the circuit. So long as your gap is relatively close to stock you'll be fine and not abusive to the rest of your system.

And since an iridium or other precious metal plug erodes more slowly, the gap will be more consistent than with the OE copper plugs.

That said I'd get some nice NGK or Denso coppers.

 

[Escape08]

https://www.supraforums.com/threads/what-spark-plugs-to-use-in-a-mk3-turbo.124528/

 

[kschachn]

I’m curious, other than a change in gap, why would the metal with which the electrodes are made change the amount of spark voltage required?

The ionization energy will depend on the cylinder pressure and the size of the gap. That’s basic physics. So, your ignition system, either exceeds that energy, or it doesn’t (in which case he will get no spark).

But as long as the electrodes are similarly conductive, the amount of voltage required to make it work is going to be the same.

A higher voltage will work more effectively, whether the spark plug has steel electrodes, platinum or iridium.

I wouldn’t get too concerned after reading that thread. It’s predicated on a great deal of misinformation.

In general, I tend to stick with the original equipment, manufacturer recommendation, and that includes heat range, electrode material, and replacement interval.

And the conductance of the tip material is irrelevant. As you note the whole concern is a great deal of misinformation. The only significant thing that precious metal tips get you is increased longevity, which isn't a bad thing. The rest is nonsense.

 

[kschachn]

Since it is not a coil on plug engine, am I better off with a copper plug and changing it out every 2 years? Will a modern iridium shorten the life of the distributor since it requires higher voltage to create spark ?

No and heck no.

I've been using precious metal tipped plugs in my old Accord for years and years and the only difference is that they last much longer.

 

[AdmiralYoda]

I've had a few late 70's/80's GM V6's and V8's and currently have a 1987 Toyota 4Runner with the 22RE. My experience is....that they all work fine as long as the gap is correct and they are the right heat range!

I've put expensive Iridium and cheapo Copper plugs in hopped up GM 305's mistaken for 350's, Turbo V6's and the same with my current Toyota 22RE 4 cylinder. No difference! The ignition systems were relatively mild compared to modern standards or modern performance alternatives. As long as you aren't burning oil or running rich you'll be fine.

When those plugs are new will you notice a performance difference? Probably not. But the fancy precious metal plugs will last longer....but not 100k longer like most modern OEM intervals.

 

[wpod]

Nice car and I would use what ever type of spark plug was oem or similar. Nippon Denso or NGK?

 

[slacktide_bitog]

The finer electrode of iridium actually requires less voltage. It will not shorten the life of the distributor.

The Denso Iridium TT is awesome! The part number you need is IQ20TT. Denso's heat range 20 is equivalent to NGK heat range 6.

If you don't want to use iridium for some reason, Denso actually makes a Nickel TT, part number Q20TT.

 

[alcyon]

Thanks, right now I have Iridiums in there thanks to my previous mechanic, only ran 45,000km thus far, i will go to 100,000km then change out to iridiums again.

 

[wlk]

I would use copper as probably oem. I have tried other types and found copper to run better in my vehicles that came with them oem. I have iridium in my 05 Honda as it came that way and will continue. Good luck

 

[alcyon]

Then again, is this chart correct ? it gives me the impression that coppers don't have good ignitability..

 

[kschachn]

I'm not sure why you would want them to ignite.

 

[slacktide_bitog]

Then again, is this chart correct ? it gives me the impression that coppers don't have good ignitability..
View attachment 244581

Denso doesn't sell the Nickel TT in the US. The Platinum TT seems to only be sold in the US/Canada. However, the Platinum TT is single platinum, hence the shorter lifespan than double platinum.

Most nickel/copper plugs have a fat electrode, which requires more voltage than the thinner ones seen with iridium and platinum. Finer electrode copper/nickel plugs exist (NGK V-Power), but they have a very short lifespan. However, the Denso Nickel TT might have a decent lifespan, even if not as good as iridium. But you should still get the iridium TT if you can afford them.

Spark plugs are cheaper here than in your part of the world. For example, the price you'd pay for the Nickel TT is we can get iridium plugs for.

The Iridium Power has iridium on the center electrode but nickel on the ground, while the TT and Long Life have platinum grounds. The power is listed as higher ignitability than the other two.

I'm not sure why you would want them to ignite.

Why shouldn't ignition ignite?

 

[eljefino]

Then again, is this chart correct ? it gives me the impression that coppers don't have good ignitability..

It's from someone who wants to sell expensive spark plugs.

 

[Asterix]

Toyota specified platinum plugs for the 7M engine, both GE and GTE. The GE has a distributor. Use platinum or iridium plugs in your 1G-GTE and be happy about it.

My 7MGE has had platinum plugs its whole life, about 288k miles at this point.

 

[SC Maintenance]

I thought the voltage needed to jump a gap was inversely proportional to the electrode size. In the case of welding with an old stick welder, you needed to turn it up to get a thicker rod to arc and hold the arc?

I thought the reason to go with exotic metals was to be able to get the center electrode smaller. At least that is my observation when comparing supposedly a replacement platinum plug to a copper plug in the past?

Thinking out loud.

 

[ARCOgraphite]

We used to cut back and file shape the GND straps on old Inconel Champions on my drag race car. No MSD back then. Ran magwire and noticed NO benefit other than a lighter wallet. We weren't running a magneto just a heavy spring single-point breaker and oil bath coil with a lowered impedance ballast and NO resistance wire (ign-ON). This works for drag only and eats points quickly. Not for street/daily. Didn't get into clocking plugs - something you could do with the heads off with the first set.

A quality spark plug cable and termination and a thick Boot was important along with a gentle radius in routing. I always ran genuine Delco which I recall was built from Packard wire stock. My co-worker used to call the Belden wire you would find at AP stores "Bedlam" for what should be now obvious reasons - things might go "haywire".

Some kind of "magic" going on in secondary ignition layout

- Arco

_______________________________________________________

GM Delco p/n: 2979303

 

[k1xv]

An electrode with a sharp tip requires less voltage to initiate a spark than a blunt electrode of a copper plug.