18mm auto plugs?

I am thinking about adding a second pmag and would like to omit the plug adapters. Searched the archives and most guys seem to cite the Autolite 386 or Champion D9, which is described as a industrial/tractor plug at Pep Boys, in 18 mm size. The info is old and I would appreciate any more recent info on using a 18mm plug in a 0-320 160hp.

Currently using NGK BR9ES and they are running fine but I am running rich so will switch to the 8's if I am not able to find a18mm auto plug that suits me.
Thanks.

JimWoo50 said:

I am thinking about adding a second pmag and would like to omit the plug adapters. Searched the archives and most guys seem to cite the Autolite 386 or Champion D9, which is described as a industrial/tractor plug at Pep Boys, in 18 mm size. The info is old and I would appreciate any more recent info on using a 18mm plug in a 0-320 160hp.

Currently using NGK BR9ES and they are running fine but I am running rich so will switch to the 8's if I am not able to find a18mm auto plug that suits me.
Thanks.

Click to expand...

I'm curious why you are running the BR9's rather than the recommended BR8ES.

Can you enlighten me?

I don't recall

For sure but I think I read somewhere on here that the 9 plug was equally well suited for use with my pmag and were a cooler firing plug. They worked fine and if they weren't so inexpensive I would put them back in, as except for a coating of soot from my last flight on which I stayed low and didn't lean as aggressively as I probably should have, they are still like new after 100 hrs. or so and no issues up to 16,500ft.

I will switch to the 8's if I don't settle on a 18mm plug just to compare. I like to experiment and learn new stuff.

We ran the 386

in the -8A (O320H2AD) with one mag and one electroair ---- worked great and changed them out every condition inspection --- glad I did not have to fool with adapters.

I have found that the brass adapters I got with my PMag are difficult to thread in. It takes me a while to get the thread properly started and I think it would be super easy to get cross threaded. I purchased a thread chaser from ATS and it helps some. Why the starter thread is cut so it is difficult to thread in is beyond me. Have no problem with my Champion plugs screwing in for my mag.

So I to would be interested in others that have used the larger spark plug on their EI so I can eliminate the adapter.

I had a couple of the brass plug adapters that were difficult to thread in. I took a jewelers file to them and smoothed out the end of the thread just a tiny bit and from then on they have been easy to hand install.

I use the Autolite 386's in my O-320 with an Electroair ignition, in the bottom positions.

I am continually impressed with how well that ignition / plug combo works, I wouldn't change a thing.

I've asked before

Hi Jim,
You are asking a valid question and one I have asked before too without a solid answer. I flew with 18mm plugs autolite 386 with my ElectroAir ignition. When I switched to PMags, I switched to the recommended BR8ES 14mm plugs with adaptors. I haven't had any issues, but would like to ditch the adaptors if I could.

A comparison between the two plugs heat range is in order.

Dan

Autolite 386 Plugs

I am using the Autolite 386 plugs with my Electroair ignition system in my O360 A1A / RV6a and they are working fine.
I don't see much point in throwing them away each annual inspection unless you are doing say 200 hours or more per year. The plugs were designed to work with tractors which probably operated for a thousand hours or more before being changed. It is obviously subjective but I have the feeling the engine runs smoother with the Autolite 386 plugs than the standard Champion aero plugs I was previously using. The only issue I have with the plugs is I can't buy them here in old Europe so have to get them shipped from the US.

Barry RV6A F-PRVM