Replaced spark plugs with NGK's in Hemi

[MagnumFreak]

Well about a week ago I bit the bullet and purchased 135 bucks worth of Iridium NGK plugs for the magnum. Finally changed them out today. Spark plug change was easy. Took about 45 minutes start to finish. Did it improve performance??? I wish I could test it right now but mother nature is busy washing the streets for us. I really don't expect any change in performance for just changing plugs. I do know that it "seems" to idle smoother. NGK part number is LZTR4AIX-11 if you go to sparkplugs.com search for part number 2313. They are about 7.60 each plus shipping. Remember there are 16 plugs in this car.

What would you imagine would be the toughest plugs to change?? Got to be the ones near the firewall right? Wrong. Front two passenger side. The extension I had was a bit too long. The power distribution box mounted on the fenderwell gets in the way. The rest were really easy, just so many of them.

Thank goodness this car is a hemi. If it had a standard engine in it changing plugs would be impossible. Not much gap between the fenderwell and head.

I didn't take any pictures but it really isn't rocket science. Each cylinder has a spark plug wire on one plug and a coil pack on the other. The coil pack removes with two 10 mm bolts. The boot for the plug under the coil is built into the coil.

New performance plug wires are on order and should be here early next week. I will post details when I get them and make sure they work.

[magnumrtawd]

lgreat , thanks for the info... let us know how it works out

[HGB7862]

OK MagnumFreak,

Did the plugs gain any HP???

[MagnumFreak]

Not any noticeable change. Car does seem to idle a bit smoother but no significant hp change.

[Wicked96SS]

What did you gap them to?

[MagnumFreak]

Can't remember right off hand. I did gap them per the service manual. It is the same gap that is on the sticker under the hood.

[HankL]

the -11 at the end of the NGK part number stands for 1.1 mm or about 0.0433 inches.

With the tiny irridium tips you probably could open this up to as much as 0.060 inches

the relatively short 1.1 mm gap is set to allow the plugs to go over 100,000 miles with the typical wear that opens the gap over time. If you are willing to regap more often, say every 30,000 miles then you can use a large gap.

The larger gap should give a bit more torque in the 1200-2200 rpm range.

If you go too big in gap, say greater than 0.090 inches, you might see some missfires above 5,000 rpm.