February 6, 200719 yr Is there an Iridium plug available for the 4RT? I seem to remember someone saying that a CR6EIA-9 crosses to the stock CR6EH-9 but it has full threads. What's with the partial threads on the stock plug?
February 7, 200719 yr 1/2 length plug avoid having thread near the chamber & hence help avoid detonation. In addition, any thread near the chamber can gather carbon, which means when you remove plug posibility exists to stuff (tech word there) the threads in the head. Many NGK plug tables are avail on net, and from that you can decode the correct definition for an iridium plug - which looks like you have correct, but best I know it's not actually available (yet?). However having said that, http://www.outperformanceshop.com/NGK_s/1923.htm lists them?
February 7, 200719 yr Author I’m not sure I entirely agree with your explanation cadman. The top half of the metal sheathing is not threaded – there is still thread at the bottom (electrode end). I don’t think it presents any less thread in the combustion chamber as far as detonation goes. I do agree that there are fewer threads to get fouled and stuck in the head though. I’ve never seen a plug like this before. It almost looks like a combination of a standard design (with gasket) and a tapered seat version. I suspect that the taper is meant to seat as the gasket compresses. This could possibly aid in heat transfer and sealing. In any case, I’m not holding my breath for an Iridium version. The plug’s been out at least since 4RTs were introduced. It’s too bad, I suspect that they would help with 4RT starting problems. I know they made a difference with my 2Ts. http://i178.photobucket.com/albums/w267/SG...3/CR6EH9VGA.jpg Edited February 8, 200719 yr by STEVEC
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