P mag plugs?

N661DJ · #1 10-11-2016, 01:58 PM

I have an IO-390 that is equipped with dual P Mags.
The engine requires long reach plugs with the long reach brass adapters.
P mag documentation suggest the NGK BR8ES plug, this plug when installed in the brass adapter is too short the electrode is 1/4" inside the adapter.
What plugs are used in this configuration?
Talked with P Mag and they said to use the DENSO IKH27 plug, tried numerous auto parts stores, no one stock that plug.
Question, Is the DENSO the only plug that will work?
Dick

Raymo · #2 10-11-2016, 02:08 PM

Amazon has them at this link.

https://www.amazon.com/Denso-IKH27-I.../dp/B000M6URAA

APACHE 56 · #3 10-11-2016, 04:35 PM

NGK LZFR5C-11 Spark Plug #NGK-92174 (long reach)

Cheaper, more accessible than Denso and I've had much better luck with them in my 390.

N661DJ · #4 10-11-2016, 06:52 PM

Good info,
Thanks Don,
Dick

Larry DeCamp · #5 10-12-2016, 06:37 AM

I am using BR8ES because so many folks have endorsed them. I had not noticed the the tip length deficit in the adaptor ( my bad ) I am approaching annual and plan replace plugs as suggested by others citing "cheap preventative maintenance and resistors do deteriorate". So, what is the expected benefit of the longer reach plug ?

APACHE 56 · #6 10-12-2016, 06:27 PM

Quote:

Originally Posted by Larry DeCamp

I am using BR8ES because so many folks have endorsed them. I had not noticed the the tip length deficit in the adaptor ( my bad ) I am approaching annual and plan replace plugs as suggested by others citing "cheap preventative maintenance and resistors do deteriorate". So, what is the expected benefit of the longer reach plug ?

Hi Larry,
as for the benefit, I don't have a clue and that's the truth. I guess a call to Alan Barrett would be your best bet. As an aside I would venture a guess that it has to do with a more efficient ignition process. A guy at Auto Zone mentioned that more autos are going to long plugs in response to my surprise that there were a number of long reach plugs in stock.
Don

868RM · #7 10-12-2016, 07:19 PM

I may be incorrect but what is considered a "long reach" NGK plug is 3/4 inch. The IO-390 plugs adapters need a plug with a 1 inch reach. I'm glad those 5 heat range plugs are working well, but that seems a little hot. I found some 6 heat range NGK's but I'm using the Denso's because of the heat range. They are 9 heat range.

APACHE 56 · #8 10-15-2016, 10:58 AM

Quote:

Originally Posted by 868RM

I may be incorrect but what is considered a "long reach" NGK plug is 3/4 inch. The IO-390 plugs adapters need a plug with a 1 inch reach. .

Here is a side by side of NGK and DENSO. The DENSO barrel is about one thread longer but the NGK is overall longer. An IA told me the long reach is a heat sink. One more opinion.

nucleus · #9 10-18-2016, 01:55 PM

The latest upgrade to the NGK Iridiums are the "Laser" Iridiums, the difference is that they plate the ground electrode with Platinum instead of Nickel.

Amazing spark plugs.

gear1 · #10 10-18-2016, 06:18 PM

I replaced the extended nose Tempest plugs with auto plugs when I installed the P-mag; at first I used the standard NGK plug used by everyone else, but then I discovered an extended nose plug used in air cooled Porsche engines, the BPR8EIX Iridium. They seem to perform better (smoother) in LOP operation. Same heat range as the non extended. The heat range seems right even with 9:1 pistons, as the plug insulator is a light tan color even when running WOT.
They are available from a number of Amazon outlets.