Odd plug gap

[Nick R]

It's rather strange, I noticed spark plugs for most cars seem to be gapped between .030 to .040, and the plugs on my cavalier's 2.2L (An old design by any measure) uses a .060 gap... I honestly cannot think of any advantage to having such a large gap. Anyone else have a car with such a large gap setting?

 

[mechanicx]

I think most electronic igntions have a gap around .042-.046. GM has used .060 on most of their DIS. A wider gap has many advantages assuming the ignition can deliver the spark at high speed or at low vacuum conditions. It's disadvantage is it a little harder on the ignition system, but GM DIS have a long life usually.

 

[rshunter]

Originally Posted By: rudolphna
It's rather strange, I noticed spark plugs for most cars seem to be gapped between .030 to .040, and the plugs on my cavalier's 2.2L (An old design by any measure) uses a .060 gap... I honestly cannot think of any advantage to having such a large gap. Anyone else have a car with such a large gap setting?

It's like GM couldn't make up their mind. They seem to have used the customer base as a large R&D experiment program. The very next year they went to an .050 gap, then an .040 the year after that. What the heck was going through their heads?

 

[Nick R]

So I might be better off running a .040 gap plug instead of a .060?

 

[rshunter]

Originally Posted By: rudolphna
So I might be better off running a .040 gap plug instead of a .060?

I'd take a closer look at the specs on the two model years. If they match up pretty closely, I can't see it being an issue. You'd also put less stress on the ignition system by running the narrower gap.

 

[mechanicx]

I think your Cavalier will run fine like most all of them do with a .060 gap. GM wasn't really just experimenting, the DIS will jump that gap no problem and most of them used that gap.

 

[Nick R]

Well I know they did a fairly major update of the 2.2 for the 98 model year including I think new rods and pistons, new intake mani and some other stuff... Humm, I think I'm gonna stick with the .060 then.

 

[Nick R]

Oh and DIS stands for Distributorless ignition system, right? How exactly do those differ from electronic ignition systems?

 

[rshunter]

Originally Posted By: rudolphna
Well I know they did a fairly major update of the 2.2 for the 98 model year including I think new rods and pistons, new intake mani and some other stuff... Humm, I think I'm gonna stick with the .060 then.

Yeah, the gap was consistent from '94 through '97. It was preceded by a .045 gap back in the '93 model.

 

[rshunter]

Originally Posted By: rudolphna
Oh and DIS stands for Distributorless ignition system, right? How exactly do those differ from electronic ignition systems?

Yep, Distributor-less Ignition System. It's your basic coil pack ignition, with cam and crank position sensors, a knock sensor, the control computer and, of course, the coil pack.

 

[dwendt44]

Back in the 70's, GM was all over the place on plug gap; with basically the same ignition system.
Buick, and maybe Cadillac, called for a .080" gap.
Others were are .055-.060".
One would think that DIS systems and especially coil over plug sytems could handle a wider gap.

 

[Kruse]

Originally Posted By: dwendt44
Back in the 70's, GM was all over the place on plug gap; with basically the same ignition system.
Buick, and maybe Cadillac, called for a .080" gap.


If memory serves me correctly, they initially called for a .080 gap, but quickly found out that spec was too wide.
It wasn't a recall, but GM told their techs to replace the .080 gaps with .060 or less.

 

[mechtech2]

It is not odd, you are just not familiar with newer cars [last 30 years].
A larger gap fires lean mixtures better.
A good way to say it is to use as large a gap as you can, with no misfires.
Gaps of up to .110" were used [factory specs], but they proved too wide.

 

[Kruse]

Originally Posted By: mechtech2

A larger gap fires lean mixtures better.
A good way to say it is to use as large a gap as you can, with no misfires.


One must be careful here.
Those wide gaps bring a hotter spark and your plug gap begins to widen exponentially.
Not to say it can't be done, but don't try it with a cheap copper spark plug.

 

[rshunter]

Originally Posted By: mechtech2
It is not odd, you are just not familiar with newer cars [last 30 years].
A larger gap fires lean mixtures better.
A good way to say it is to use as large a gap as you can, with no misfires.
Gaps of up to .110" were used [factory specs], but they proved too wide.

I assume you intended to respond to someone else, as I never claimed that large plug gaps are odd.

 

[The_Jeff]

Originally Posted By: rudolphna
Oh and DIS stands for Distributorless ignition system, right? How exactly do those differ from electronic ignition systems?


You can have a standard distributor and have electronic ignition with one coil. This is an evolution from the mechanical points distributors.

DIS has enough coils for the cylinders so there aren't any moving cap & rotor parts.

To further obscure your question Saturn retroactively decided .040 was better than .060 for their 96 S-cars and printed new underhood emissions stickers indicating same. Oddly, if one tries to buy an AC/Delco plug for that car under the part # they give, noone can turn one up as it's pregapped for the old spec.

 

[GMBoy]

Stick with whatever gap is shown underhood on your tune-up label.

 

[mechtech2]

rshunter -
Didn't it cross your mind that I was responding to the original post about 'Odd Plug Gap'?
No clue?

 

[rshunter]

Originally Posted By: mechtech2
rshunter -
Didn't it cross your mind that I was responding to the original post about 'Odd Plug Gap'?
No clue?

Well, I had mentioned the strange inconsistencies in GM's recommendations. Not to mention that you can never tell around here. I just wish the system didn't automatically reference another post when someone posts a "Quick Reply", as you can never be sure whether or not it was a direct reply. More than once, I've had another take offense to a comment that had nothing to do with anything they'd stated...

 

[Nick R]

Originally Posted By: eljefino
Originally Posted By: rudolphna
Oh and DIS stands for Distributorless ignition system, right? How exactly do those differ from electronic ignition systems?


You can have a standard distributor and have electronic ignition with one coil. This is an evolution from the mechanical points distributors.

DIS has enough coils for the cylinders so there aren't any moving cap & rotor parts.

To further obscure your question Saturn retroactively decided .040 was better than .060 for their 96 S-cars and printed new underhood emissions stickers indicating same. Oddly, if one tries to buy an AC/Delco plug for that car under the part # they give, noone can turn one up as it's pregapped for the old spec.


Thats strange because Amazons website says it is a Distributorless ignition system.