I asked about this a while back and got all of zero replies, so:

I finally got to do my 100kmile tune-up and install the Performance Distributors/Davis Unified Ignition Screamin' Demon coil with the plugs I selected, NGK Iridium IZFR6K13 (6774) which are designed for .051" gap and which I set to .058". I also installed the Davis Live Wires, and their cap and rotor.

It was a stuff job to get all of those fat boots seated on the cap, but with a bit of holding my mouth right they all went on. The wires are big buggers that won't fit the stock looms and are too short to route per the TSB, but they don't seem to need to be routed per the TSB anyway. I've not seen any indication of inductive cross-fire even though many of the wires run parallel for several inches and the only ones I took care with were 5 and 7.

This setup works well, and with around 600 miles on the plugs, 500 of which was sustained highway 70-80MPH and with a few good long hills to make the engine work for it, the insulators are just as white and clean as they were when they went in. It's just visible on the electrodes that they've been run, and I'll be pulling them every few thousand miles to check for wear until they've got around 20k miles behind them. I'm a bit concerned that they may erode too rapidly at .058" but will let time tell the tale.

The truck seems to like the setup, but my standard for comparison is skewed because the old Champion truck plugs that came out, while in beautiful condition, were all gapped too wide at .047" - .048". The engine pulls strong with no indications of a miss or weak firing from idle to 5200RPM at WOT through the first two gears -- I'm not at all interested in seeing rev limit in third gear.

So, if you're interested in upgrading with a Screamin' Demon and don't like the idea of cracking the gaps of the Autolites to .060" or beyond, the NGK IZFR6K13 seems to be the hot ticket. Even if it is specific to a freakin' Honda engine.

 

Now are those plugs a colder heat range than the factory Champions?

 

with that big of a gap with no MSD box , im sure thats a pretty weak spark did you try the stock gap ?

 

Yep, they're one step colder than stock, and just what I wanted with the tuner setting up a more aggressive timing curve.

The Screamin' Demon coil is much, much hotter than the stock unit (or the cheesy Accel, which is the same voltage as stock but with more energy storage which increases the spark duration). Performance Distributor recommends a gap of .060" to .065" for that coil with platinum plugs, so .058" is a bit tight. I stopped at .058" because don't want to bend the ground electrode too far back and present its sharp edge to be eroded. That's why I don't like the idea that Performance Distributor puts forth of gapping the Autolite platinums that far -- the sharp edge of the ground electrode lands right over the hemisphere of the center electrode, and the gap would be certain to grow very quickly due to erosion.