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Spark plugs io390 with P Mag

The Denso IKH27 is also known as the Denso 5347. Rock Auto has them for $7.98 Sparkplugs.com has them too @ $10.74
 
Denso Denso 5347 IKH27 which comes with a solid terminal. There are other Denso IKH27 which comes with the screw type terminal which is less preferred.
 
There is no need to run Iridium plugs. Most are using NGK BR8ES (3XXX) and changing them every 100 hrs / annual for about $2.50 ea.

Another reason for replacing every 100 hrs / annual is that you'll have a tough time re-installing them in the adapter (if not impossible) after cleaning, and cleaning Iridium plugs is not the same as cleaning the old massive plugs.

If your cylinders are made such that you don't require the adapter, running Iridium might make sense.
 
There is no need to run Iridium plugs. Most are using NGK BR8ES (3XXX) and changing them every 100 hrs / annual for about $2.50 ea. SNIP

The IO-390 (like other angle head Lycoming engines) needs long reach plugs (like the IKH-26). The BR8ES is short reach, for parallel valve Lycoming engines.

Carl
 
The IO-390 (like other angle head Lycoming engines) needs long reach plugs (like the IKH-26). The BR8ES is short reach, for parallel valve Lycoming engines.

Carl

Just as a heads up to everyone, I've been using the short reach BR8ES plugs now for several years and 715 hours in the long reach adapters in my IO-390 and have had no problems whatever.

I just received a second P-Mag to replace the impulse-coupled Slick mag I have on the other side and plan to use these plugs in both of them.

I am aware there may be a hypothetical risk of pre-ignition from a glowing particle residing on the lower threads of the long adapter when short plugs are used, but I've never experienced it. Although I fly mostly at high altitudes here in the west, I've routinely operated everywhere from sea level to 18,000 feet and see no reason not to use the less expensive plugs and replace them every year.
 
What spark plugs are people using in the IO 390 with P Mags?
I have used the Denso KH27 and switched to the NGK 6240, both are Kryptonite impregnated etc from their marketing departments. Seriously, no issues with either one. I would stick with a long reach plug.
 
Non Iridium or Platinum Long Reach

Anybody know of a long reach automotive spark plug for the IO-390 that’s the standard nickel; NOT iridium, platinum or unobtainium?
 
PIREP: Short reach adapter and plug in long reach application

IO390 angle valve engine (450 hrs.), from the beginning I have been using short reach plugs and adapter in my engine. (Requires long reach) Did not realize this was incorrect and just used what was sent to me. (My mistake, 5 years ago I didn't know what I didn't know) After reading a recent thread checked mine next oil change and saw I needed LRP's. 2 friends with similar set-ups also had incorrect adapters and plugs installed. Today replaced with LR adapters and long plugs. When I removed the old adapters, I could see quite a lot of carbon build-up in the threads that were not being used. Used a small vacuum hose down one plug and used a thread chaser to clean them up. PITA, after 2 hours finally had all 8 clean. Most took 5 to 6 tapping and removing and cleaning the chase and reoil. Mag checks produced less RPM drop than before and running on one electronic unit could hardly tell I was only firing on one plug. Have not flown it yet and will check the data on Savoy soon. Results may vary. FYI
 
The IO-390 (like other angle head Lycoming engines) needs long reach plugs (like the IKH-26). The BR8ES is short reach, for parallel valve Lycoming engines.

Carl

Always a good idea to check the source -- see https://www.lycoming.com/sites/default/files/attachments/SI1042AH%20Approved%20Spark%20Plugs.pdf

All of the -390's need long reach plugs, double check the paint markings to be certain. However, not ALL angle valve engines use long reach plugs -- for example IO-360-Axxx, C, D series use REM38E -- short reach plugs.
 
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RPM drop

IO390 angle valve engine (450 hrs.), from the beginning I have been using short reach plugs and adapter in my engine. (Requires long reach) Did not realize this was incorrect and just used what was sent to me. (My mistake, 5 years ago I didn't know what I didn't know) After reading a recent thread checked mine next oil change and saw I needed LRP's. 2 friends with similar set-ups also had incorrect adapters and plugs installed. Today replaced with LR adapters and long plugs. When I removed the old adapters, I could see quite a lot of carbon build-up in the threads that were not being used. Used a small vacuum hose down one plug and used a thread chaser to clean them up. PITA, after 2 hours finally had all 8 clean. Most took 5 to 6 tapping and removing and cleaning the chase and reoil. Mag checks produced less RPM drop than before and running on one electronic unit could hardly tell I was only firing on one plug. Have not flown it yet and will check the data on Savoy soon. Results may vary. FYI

Reviewed logs on Savoy, RPM drop with SRP and SR adapter previous 10 flights was 50 - 60 RPM. With LRP and LR adapters today was 20. Worth the effort to go to these. Test flight today engine was very smooth.
 
Always a good idea to check the source -- see https://www.lycoming.com/sites/default/files/attachments/SI1042AH%20Approved%20Spark%20Plugs.pdf

All of the -390's need long reach plugs, double check the paint markings to be certain. However, not ALL angle valve engines use long reach plugs -- for example IO-360-Axxx, C, D series use REM38E -- short reach plugs.

Mine IO-390 EXP119 was delivered from Lycoming with Denso IKH27. Do I understand correctly that I should be using different spark plugs?
 
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