What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Denso IKH 27 Spark Plugs

bmarvel

Well Known Member
Friend
Am wondering if anyone has found an alternative to the long reach Denso IKH 27 spark plugs normally used in the IO-390 with P-Mags. The latest NAPA price is $17.00 each and while still much less than aircraft plugs, it makes me wonder if there is a Plan B out there anywhere.

I previously used the BR8ES short reach plugs in the long reach IO-390 adapters and they are inexpensive and worked well. However, I was never happy with the fact they did not fill the entire length of the long reach adapters.
That left some adapter threads exposed to combustion and I was concerned about the possibility of it causing pre-ignition.
 
sparkplugs.com

Am wondering if anyone has found an alternative to the long reach Denso IKH 27 spark plugs normally used in the IO-390 with P-Mags. The latest NAPA price is $17.00 each and while still much less than aircraft plugs, it makes me wonder if there is a Plan B out there anywhere.

I previously used the BR8ES short reach plugs in the long reach IO-390 adapters and they are inexpensive and worked well. However, I was never happy with the fact they did not fill the entire length of the long reach adapters.
That left some adapter threads exposed to combustion and I was concerned about the possibility of it causing pre-ignition.

The Denso IKH 27 spark plugs are $11.93 here.
https://www.sparkplugs.com/denso-5347-ikh27-iridium-power-spark-plug

They also have a nice look-up tool for reverse engineering plugs to find what you are looking for. https://www.sparkplugs.com/search/reverseengineer?ptid=8 I didn't see many other options with a 26.5mm reach.
 
Those are good plugs, the IKH. I have some ready to go and a friend has switched already, his airplane to the TT versions of the Denso plug. The difference is the electrode is iridium on both top and bottom electrode.
Of course, we're not looking to save a couple bucks per plug, but to get the best performance, best wear and longest life.
I know I have them for my IO-540 but I think I also was able to get long-reach versions for my IO-390. The heat ranges, while different, are fine for the plane.

iridiumtt
 
I’ve been using the iK24 plug (5311) because I have normal compression. For higher compression you would use the IK27. Note to readers: this is on a. Ip-540 not the 390. My friend has used the IK20TT (4702) for the past couple years and they are looking great. I have purchased those for my next change but just waiting another year or so to swap them since mine aren’t used enough yet.
So I would say go for the TT plugs if you want all iridium electrodes.

In my IO-390 I use IKH27 (H=long reach) (5347).
I will switch to IKH20TT for that one later.
 
You beat me to it but yeah, spark plug counterfeiting is actually a big and real thing.
I called them at sparkplugs.com and talked to them to verify their supply chain.
I think they buy direct from denso. Been a while since I asked them, but they guaranteed me they would be genuine. So use a good supplier.
 
This may help to identify counterfeits. There are enough out there that Denso published this information
 

Attachments

  • Plugs.pdf
    378.2 KB · Views: 317
Thanks for posting the Denso chart. I just bought a set of IKH27 plugs for my next change from the big on-line distributor and was not aware counterfeit plugs were so common. I’ll have to see if I got taken. :confused:
 
I got a batch of forged plugs from Amazon. Pretty easy to tell as they did not even package them. 6 plugs dropped into a baggie.
G
 
Back
Top