NGK Spark Plugs

Ran into an interesting situation over the weekend while performing my annual maintenance/inspection. I had order eight new NGK DCPR8E spark plugs from Aircraft Spruce back in April. When I installed them Saturday, I discovered that the caps on the ends would not screw off. Actually ruined one plug trying to remove the cap.

As we all know, the Rotax 912ULS plug wires will only accept the small diameter threaded stud when pushing the boot onto the spark plug. The cap is too large to fit in the connector inside the boot.

So, I laid out an old spark plug and new spark plug side by side to see what gives. The part numbers are identical; yet the new plugs are unusable with their permanent caps.

What am I missing here? Anyone else have a similar experience?

NGK makes many of their plugs in solid and screw off versions. AC Spruce lists both on their site. see...

https://www.aircraftspruce.com/catalog/eppages/ngk.php?clickkey=2454637

NGK's park number for the ones with the removable nut is 4339. Yours are probably 4179. Both are DCPR8E. I made the same mistake a while back when buying the NGK BR8EIX.

Bevan

Hi Bevan,

I think you have your numbers backwards. The NGK DCPR8E (4339) (912ULS) are the ones with the screw off tops.

NGK 4339 DCPR8E Standard Plug

BRAND : NGK

Plug Specifications

Thread Size: 12mm
Hex Size: 5/8" (16mm)
Reach: 19mm (3/4")
Seat Type: Gasket
Gap: .028" (0.7mm)
Heat Range: 8
Terminal Type: Removable Nut
Resistor: Yes
Thread Pitch: 1.25mm
Brand: NGK
Center Electrode

Type: Standard
Material: Nickel
Size: 2.5mm
Projection: Projected
Ground Electrode

Type: Standard
Material: Nickel

You are correct...

NGK 4339 are Removable terminals
NGK 4179 are Sold terminals

I will correct my post for the archives.

Sorry for the confusion.

Bevan