BleedinBlue

I have changed the plugs in my previous cars several times, and have never checked the gap on a plug in my life. Is it absolutely necessary? I thought they were correctly gapped from the factory.

Another thread has motivated me to change my plugs today, if I don't need to regap the plugs I don't need to go to the store

BleedinBlue

Ok...due to the overwhelming responses I went ahead and got a gap tool. [:-]

Derf00

Always a good tool to have handy anyways (Plug gapper) be sure to get feeler gauges though vs the wire ones. More accurate with feeler gauges and they have more uses.

I never trust what the aftermarket says about NOT gapping their plugs unless I buy motorcraft. Problem is that many aftermarket plugs are universally gapped.

Example. Stock gap on my Mustang 3.8L is .052-.054. Motorcraft comes gapped at that.
Crossreferenced plug say Bosch or Denso Iridium come gapped at .044 and their website states .050 for the gap on my car yet also state no gapping required. go figure. I gapped them and they run like champs!

sweet99

I use NGK platinums for the Mustang and they are pre gapped. Great plugs too as I actually gained a tenth with them! maRK

BleedinBlue

Mine are autolite double platinums. What should the gap be? .050, I think I read here somewhere, that right?

P Zero

The wire ones are for the special tipped plugs such as iridiums, and double platinums. If the have a normal style electrode, feeler guages work just fine.
-P.
PS: ALWAYS check the gap, I dont care if theyre motorcrafts, they could be off. What if the parts guy dropped it?

Derf00

Never said not to check them...

stang2000

Always check your gap. I have an 00GT and the stock gap is .054, well when I bought my NGK TR6's they were all pregapped at .035 which is fine since I have a supercharged application. So I'd say always check em.

BleedinBlue

I'm done. I gapped them at .050. Out of the box they were a tad bit wider than .040.

Ahhh...and the difference the new plugs made...DAYUMMMMM. The idling is slightly smoother, not much change there. But I just took it for a short test drive and did by far the longest brake-less burnout I have ever done in this car. I swear I didn't think they were ever going to catch. Unless I drove through a puddle of oil and didn't realize it, j/k, the new plugs were definitely a breath of fresh air for her. Too bad I waited so long to put them in.

Poobs

The voltage required to jump the gap goes up tremendously as the plug gap is increased. The same requirement also goes up with engine load.

On a modern engine it is near impossible to make them misfire because electronic ignition is so powerful and the fuel mixture is well controlled.

Theoretically if the gap is set too wide you could reach a point where there is not enough power to jump across the gap.

This would take place most often on worn plugs that are coated with build up and worn electrodes as you try to accelerate.