I had read in a thread here that the “best” ultimate spark plugs for our engines was:
NGK Iridium BPR6HIX
And the next best was:
NGK Platinum BP6HVX
So I went to my excellent local auto parts store and they didn’t stock either of them, but they cross-referenced and said that they did have these Denso’s which they said were the equivalent:
Denso Iridium IW20 (5306)(I06) – the last two were other designators on the box.
I have a high energy MSD ignition system and I wanted to increase my plug gap because of this, so why not upgrade the plugs at the same time. They came with .040” gaps which suited me just fine. My previous plugs had less than 5000 miles, but had weathered all my timing, carb, and upgrade adjustments since I’d gotten the car 5 years ago, so a clean slate with the best possible new plugs seemed warranted. My old plugs(which were the correct light brown color, indicating that my air/fuel ratio was in the proper range), gapped at .030-.035”, were:
I put the new plugs in and they work just fine. I’ve only driven a low speed 10 miles with them. I seem to idle a bit faster and run a tad smoother, which seems to indicate that I’m burning gas more efficiently. I noticed that the threaded part of the new plugs was ¼” longer than the Champions and I felt them “push through” some built up deposits, where the previous plugs had reached their insertion limit, while installing them. They performed as advertised so I was happy.
Then that darn Mike Notigan emailed me with concern that plugs that were too long would affect my wave fronts and eventually give me trouble with hot spots from carbon build up and such. Dang him! Dang him to heck! My initial euphoria was popped like a bubble gum blow out all over my face.
I had a spare unrestored 2.0 head in the basement, so I just got done installing both plugs to see what we shall see. Yup, the new plugs stick a whole ¼” into the combustion area. Below are pics.
So my question is: Is this totally unacceptable? I should return them, right? They probably increase my compression a little(Wheeeee!). Should I keep them?
Would the NGK Iridiums listed above have been the proper length?
Please help me out in obtaining the “ultimate plug” for street use in a moderately jacked up 2.0 engine.