Why .048 gap on plugs
- Thread starter bhans40
- Start date
opalescent 96
New member
You're more likely to have a miss fire with a wider plug gap. It's harder for the spark to jump the gap under high rpm and high cylinder pressure. A wider plug gap is emission related and gives you more spark and a hotter leaner burn. You can get a potential spark nock from the wide gap and lose power.
The people you run a .048 gap most likely have a tune that has more timing added etc. For a stock tune I would recommend a .050 plug gap
The people you run a .048 gap most likely have a tune that has more timing added etc. For a stock tune I would recommend a .050 plug gap
.048 because then the plug will "wear into" the stock .054 gap.
if you start wider, your plug will have a shorter service life.
so its just a way to run the plugs a little longer than normal without regapping.
most cars will notice no difference with that small of a difference in plug gaps.
if you start wider, your plug will have a shorter service life.
so its just a way to run the plugs a little longer than normal without regapping.
most cars will notice no difference with that small of a difference in plug gaps.
Gau8mechanic
New member
I figured it was because those running .048 had boost of some kind and did that so the spark wouldn't blow out.
So would .050 also help with a high mileage engine?
So would .050 also help with a high mileage engine?
driller
El Presidente
The stock gap was prescribed for the stock platinum spark plugs which had a long service life. Copper plugs will have a longer service life starting with a slightly smaller gap as was said.
Technically you will get a better flame front from the widest gap possible for reliable spark from the ignition. High combustion pressures from performance enhancements necessitates a smaller gap than stock but that's usually around 0.035" to 0.040".
Consider the scale below:
0.056....worn
0.054... stock
0.052.
0.050..
0.048... copper
0.046
0.044
0.042
0.040.
0.038..
0.036... boosted
0.034
Technically you will get a better flame front from the widest gap possible for reliable spark from the ignition. High combustion pressures from performance enhancements necessitates a smaller gap than stock but that's usually around 0.035" to 0.040".
Consider the scale below:
0.056....worn
0.054... stock
0.052.
0.050..
0.048... copper
0.046
0.044
0.042
0.040.
0.038..
0.036... boosted
0.034
opalescent 96
New member
My old 1993 Crown Victoria 4.6 had the same .052-.056 gap specification. I don't believe it came with platinum plugs from the factory so I don't think the gap was prescribed for platinum.
I agree with gaping a little smaller that specified for longer service life but going from a .048 to .056 is a lot of wear on the electrode between plug changes. That means you're getting a lot of heat in the cylinder and a possible lean condition. I guess it depends on the mileage but hopefully it's a lot.
A smaller gap is better for performance/rpm/pressure and you can run more timing with a smaller gap. But in a Mark VIII you need to strike a balance because the timing isn't adjustable like an old car with a distributor. (unless you have a tune) If you go too small on the gap you'll lose power from the smaller spark.
I agree with gaping a little smaller that specified for longer service life but going from a .048 to .056 is a lot of wear on the electrode between plug changes. That means you're getting a lot of heat in the cylinder and a possible lean condition. I guess it depends on the mileage but hopefully it's a lot.
A smaller gap is better for performance/rpm/pressure and you can run more timing with a smaller gap. But in a Mark VIII you need to strike a balance because the timing isn't adjustable like an old car with a distributor. (unless you have a tune) If you go too small on the gap you'll lose power from the smaller spark.