Spark Plugs: The pre-gapped myth. (parts rant)-Page 2: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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April 25, 2011 4:45 p.m. Keith SuperDork

dculberson wrote:

This thread got me as I just replaced the plugs on my turbo Volvo 850. All 5 plugs were gapped wrong according to the measurement on the box. Turns out the box marking was incorrect and I gapped the plugs wrong. Huh. Car's running great. Factory calls for .028" and I gapped to .035". Should I re-gap or leave it at the higher gap?

If you're not getting misfires, I'd leave it.
April 25, 2011 9:49 p.m. mmosbey New Reader

racinginc215 wrote:

I've never gapped the plugs on my RX7.

Same here.
April 25, 2011 10:51 p.m. daytonaer Reader

Bench Racer (BowtieBandit) wrote:

Why do people assume that all spark plugs are pre-gapped?

/rant.

I gapped a set of platinum plugs with a feeler gauge, ran ok then ran like poo after a few thousand miles. Parts man said "Platinum's are pre-gapped, you ruined them"

I recall reading something about platinum plugs being sensitive to feeler gauges, and if you are going to gap them only to use a tool which does not scrape the Pt surface. As I really only have ramp or go/no go tools, I just stuck them in as is. Actually I prefer copper plugs which I habitually check the gap on.

I'm assuming that's where it originated, better to run the pre-set gap on fancy metal plugs than risk ruining the precious metal surface treatment with a ramp style feeler, thus pre-gapped, or don't touch it.
April 26, 2011 9:18 a.m. dculberson Reader

Keith wrote:

If you're not getting misfires, I'd leave it.

Thanks, I'm not, so I will leave it, unless something goes wrong!
April 26, 2011 9:22 a.m. 93EXCivic SuperDork

daytonaer wrote:

Bench Racer (BowtieBandit) wrote:

Why do people assume that all spark plugs are pre-gapped?

/rant.

I gapped a set of platinum plugs with a feeler gauge, ran ok then ran like poo after a few thousand miles. Parts man said "Platinum's are pre-gapped, you ruined them"

I recall reading something about platinum plugs being sensitive to feeler gauges, and if you are going to gap them only to use a tool which does not scrape the Pt surface. As I really only have ramp or go/no go tools, I just stuck them in as is. Actually I prefer copper plugs which I habitually check the gap on.

I'm assuming that's where it originated, better to run the pre-set gap on fancy metal plugs than risk ruining the precious metal surface treatment with a ramp style feeler, thus pre-gapped, or don't touch it.

I never knew that.
April 26, 2011 9:22 a.m. hotrodlarry Reader

I'm assuming that's where it originated, better to run the pre-set gap on fancy metal plugs than risk ruining the precious metal surface treatment with a ramp style feeler, thus pre-gapped, or don't touch it.

correct.