Denso Iridium TT Spark Plug Gap

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Y_K

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I am trying the Denso IT16TT (4713) on my Towncar and it works fine. Panthers traditionally require 0.54 inch gap (1.4 mm). The Denso plugs come in at 0.40 preset from the factory, and I have verified that. I am confused after all the reading I have done as to whether I need to re-gap those or just leave them be. Hence, my request for the collective wisdom, based on practical experience. Similar Denso plugs look like new after 120k miles on my Landcruiser, That is why I decided to try them on a panther.
 
Iridium is a very hard, brittle material. Re-gapping (you should check, though) is not recommended as you may create cracks or actual breakage, now or sometime after installation.

0.54 is a fairly large gap for a modern OEM recommendation, but it's not out of the realm of practicality ... an electronic ignition in good condition should be able to cross about 0.60 with typical street vehicle compression ratios and maximum RPMs. On the other hand 0.40 is not "too close" ... the plugs will work fine with that gap, again with any modern electronic ignition.

There are advantages to having as wide a gap as possible, but then again there is a line where you start to get misfires. Unless you have a highly tuned high compression race motor, the added value of that extra 0.14" isn't critical (it un-shrouds the spark a little, which in theory makes it easier to light the charge, but if you're not misfiring, which you should notice as roughness, it's lighting the charge just fine).

Use the pre-gapped plugs and stop worrying. Your car will probably be just fine with it.

If you happen to be running a points-style mechanical ignition ... rare, these days; even Big 3 motors have had electronic ignition since the 1970s as standard ... then maybe 0.32 might be more to the engine's liking. Or the other option is magneto ignition, again rare unless a purpose-built race engine, likes a big gap but will misfire at lower RPMs, where the engine's purpose isn't relevant (such as drag racing) or it's done for style reasons (hot rods, custom big motor / super-lightweight motorcycles). Neither is likely to apply to you, or anyone for that matter who doesn't know exactly which gap they want to run.
 
Is the ground electrode iridium? I thought it was only the center electrode. The ground electrode should be able to be bent slightly without cracking or breaking.
 
The Denso TT Iridium have a platinum pos pad with a copper core and iridium neg pad on a steel strap. I use then in my Gen Coupe and have to close the gap from the pre gapped .043" to around .030". Use a needle nose or tool designed to bend the ground strap to spread the gap. Just tap them on a hard surface to close the gap.
 
Originally Posted By: d00df00d
Is the ground electrode iridium? I thought it was only the center electrode. The ground electrode should be able to be bent slightly without cracking or breaking.


TT's are twin tip, so it's iridium on both the center and ground.

Yes, having the right tool for the job helps prevent damage to the plugs, so it's the feeler gages with the slotted arm to bend the ground electrode.
 
Denso doesn't specify gapping on these - with that said, I gapped a set of Platinum TTs to .033"/.8mm per OEM spec. If you're dropping them into a modern Toyota/Honda or anything that calls for a .044"/1.1mm gap I think you should be fine out of the box.
 
I like the TT line of plugs and have used the Iridium TT and Platinum TT plugs with good results. I usually use Autolite or NGK but started also using Denso plugs last year.
 
Originally Posted By: Y_K
Panthers traditionally require 0.54 inch gap (1.4 mm). The Denso plugs come in at 0.40 preset from the factory, and I have verified that.


Are you sure it's not 0.054 and 0.040 inches?
 
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