Tempest Iridium Fine Wire Spark Plug URHM38S

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Single Plug Box of 12 Plugs
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Aviation Spark Plug With the most automated manufacturing processes and the most innovative spark plug in the aviation industry. Made in USA.

High Conductivity Copper Core Center Electrode copper, co-extruded inside a nickel alloy sleeve ensures outstanding heat and electrical conductivity while the nickel sleeve offers high resistance to corrosive combustion gases.

High Alumina Ceramic Insulator high mechanical strength, superior dielectric properties, proprietary protective glaze, provides high performance to conquer severe operational conditions. "Clean Collar" massive electrode "V" tip focuses heat to reduce fouling and enhance heat range control.

Proprietary Glass Center Seal 21st century 'fired in' resistor replaces the multipart screw, spring, carbon pile stack up used in competitive plugs and known to suffer from resistance value instability that can cause misfires, wasted fuel, engine roughness.

Nickel Finish environmentally preferable electrolytic nickel provides outstanding durable finish, superior corrosion protection, and extreme wear resistance.

Nickel Ground Electrodes aviation grade nickel electrode design focuses on minimizing sparking voltage requirements while maintaining specification gaps to ensure large, stable 'flame kernels' for on-time ignition and complete combustion.

Vacuum Infused Center Electrode proprietary, vacuum infusion process seals electrode/insulator gap providing stable heat range and superior center electrode cooling (heat flow to the insulator).

Hot-Lock Assembly intense pressure and heat create positive, zero-leakage, shrunk in seal between insulator and shell to contain the hot, high pressure combustion cycle gases.

Harness Wire Contact smooth, uninterrupted, oxide treated spring contact surface offers enhanced corrosion resistance, is chemically bonded to the fired-in resistor providing the ultimate harness/spark plug termination integrity and energy transfer.

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Fast shipping, great product!

Harley G Verified Purchase


December 21, 2021

Product arrived on time and as ordered!!

John C Verified Purchase


November 27, 2021

Exactly as advertised. Adjusted the gap slightly and worked perfect. Broke the fine wire on an old plug and needed one replacement.

Paul J Verified Purchase


June 2, 2021

Expensive for sure. Im getting faster starts on my Mooney. Think its running a little smoother lean of peak as well. Time will tell--those with Mooneys that have these installed with the Surefly ignition are having impressive results--I hope to go that route next.

January 28, 2021

I have been an A&P for 30 yrs. I have found Tempest spark plugs to be perfect every time. When I ask customers to replace their plugs they have all told me after their first flight with the new Tempst plugs that the engine runs so much more smooth.

John L
July 20, 2020

First off, very quick shipment. The quality of the valves will be a test of the manufacturer and we will see what the service life is....but that has nothing to do with spruce

Lawrence N
June 29, 2020


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Do I need 18mm or 14mm gaskets for this Tempest Spark Plug (URHM38S XL)?

The Tempest Fine Wire URHM38S XL spark plug uses an 18mm gasket.

Q: What is the difference between the Tempest URHM38S and the URHM38S XL designation?

There is no difference. They are one and the same.

Q: I currently have Champion REM38E plugs on Lycoming )360 A4M and would like to get Tempest fine wire plugs, which model would fit?

The correct fine wire model to replace the REM38E plugs is the UREM38S.

Q: i have a pa-28-180 o360 a4a and use urhm38e what fine wire tempest plug should i order?

URHM38S would be the replacement fine wires for the URHM38E massive plugs.

Q: I have RHM40E, is the URHM38S XL the correct replacement?

RHM38E would be an equivalent to the URHM40E. The only difference is the 38 has the lower heat rating position.The URHM38S is a fine wire plug. The RHM40E is a massive plug.

Q: What size socket does the Tempest XL URHM38S take?

7/8" socket, like our part number 12-01693.

Q: Do these massive Tempest spark plugs come pre-gapped?

Yes, massive plugs are gapped .016.

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