Pmag with auto plugs in long reach heads

Anyone have experience using a pmag with a long reach plug engine? Brad Dement with E-Mag relayed to me that they have had customers and engine shops using the standard short reach assembly in long reach heads with good results. Their install instructions indicate that the auto spark adapters have not been tested with long-reach plugs. They suggest that the auto spark is a superior solution for the setup and indicate that 80% go with auto plugs.

Lightspeed sells two different insert adapters for standard and high performance auto spark plugs and I have seen a reference from someone suggesting these inserts with a pmag. Their literature suggests that only long reach plugs should be used in long reach heads.

Electroair uses a different type of spark generation system and suggests that you should continue to use aircraft massive plugs with a larger gap.

After too much research I need to find out a bit more on the Pmag with auto plugs in long reach heads to move forward.

I see no reason why you couldn't use Lightspeed's solution (plugs and inserts) with P-Mags.. it's not like PMag knows anything about "reach"

I've been using the Emagair adaptors with long reach auto plugs for just on 100 hrs now. And have had the plugs out and in through several services now. And all is still good with no problems.
I torque'd the adaptors 2 lb more than was recommended and torque'd the plugs 2 lb less than recommended. I have never have a plug come loose or an adaptor come out with the plug yet.
"Touch wood", everything keeps behaving.

what plug and engine?

RetiredRacer said:

I've been using the Emagair adaptors with long reach auto plugs for just on 100 hrs now. And have had the plugs out and in through several services now. And all is still good with no problems.
I torque'd the adaptors 2 lb more than was recommended and torque'd the plugs 2 lb less than recommended. I have never have a plug come loose or an adaptor come out with the plug yet.
"Touch wood", everything keeps behaving.

Click to expand...

What engine and plug are you using?

Sorry to be so long getting back to you Steve, but I have been busy out at the hangar getting the RV ready for painting.

Lycoming 0-235 low compresion C2C.
NGK BR7ES

[email protected] said:

Lightspeed sells two different insert adapters for standard and high performance auto spark plugs and I have seen a reference from someone suggesting these inserts with a pmag. Their literature suggests that only long reach plugs should be used in long reach heads.

Click to expand...

A short plug in a long thread cavity is not the best set-up for flame propagation in the combustion chamber. One of the advantages with running auto plugs is exposing the electrode in the combustion chamber for better flame propagation when ionization (spark) a cures.

long reach auto plug adapters...

G3i Ignition said:

A short plug in a long thread cavity is not the best set-up for flame propagation in the combustion chamber. One of the advantages with running auto plugs is exposing the electrode in the combustion chamber for better flame propagation when ionization (spark) a cures.

Click to expand...

This makes sense... I have ordered a set of standard and long reach plugs tha should work well (Denso IK27 and IKH27) and hope to get ahold of some long reach adapters for comparative testing. I placed and order for some from light speed but the order has not been filled... I have heard that they will not provide them for use with other systems... Brad with pmag says that they make their own in house and can make them any length but have not seen a need. I have requested a set for testing and hopefully they will make them available.

Another possible source is http://www.sparkplugadapters.com/services.html who make adapters for tractors. I received an email from John, the owner, who said he could make them any length needed but preferred to make them from steel.

Are long reach plugs really needed? I don't know... with massive aviation plugs the answer is more clear; with the hotter and longer spark over a wider gap there is some reported success with standard plugs. It sure seems that placement of the spark tip within the combustion chamber would be a factor in the performance of the system though.

long reach and standard auto assembly

Just about finished installing my pmag. Much more time tying up wiring than I expected but that seems to be the way of things.

Here is a shot of a long reach massive aviation plug next to a standard auto plug installed in an insert. The aviation plug was sitting on the shelf, not from the engine, rusting away from the lovely northwest weather.


For comparison a long reach auto plug (26.5 mm reach) installed in the insert is very close to the same length as a long reach aviation plug. I hope to have some longer adapters soon...


RED wires!

Plug Adapters

I installed a pmag on my IO-390/Giles 200 (long reach/angle head) a while back, but didn't have the long adapters, so used short adapters and short auto plugs. It ran fine, better than the mag for sure. Recently I bought some long adapters and iridium plugs from LSI and changed them over. I had to clean the threads in the head quite a bit to get the long adapters to screw in easily. I'd suggest not a good idea to erode these threads through extended use in this configuration.

I picked up an LSI Plasma II Plus kit recently and am in the progress of installing it on the RV-4/O-360-A1A, so can use the short adapters and plugs there.