Aviation Champion spark plugs don't have the best benefit-to-cost ratio:

  • Rapid fouling during ground ops
  • Insulator sometimes cracks during transition from ROP to LOP
  • The resistor usually fails within 3-4 years of service (you need to discard the plug if it's more than 5K Ohm)
  • Quite expensive - you can buy 16 NGK spark plugs for the price of one (!) Champion spark plug
  • Two electrodes make spark plugs more prone to fouling
  • Bad spark plug resistors lead to burnt points and magneto coil overheat

This spark plug adapter makes it possible to use modern automotive spark plugs in Lycoming & Continental aviation engines instead of REM/RHM series, like REM38E or RHM40E.

  • It adapts a 18mm x 1.50 spark plug hole to a 14mm x 1.25 female thread

            • Modern automotive spark plugs have greatly evolved from tractor era engines 
            • Automotive spark plugs are more reliable and capable of running in much worse conditions
            • The adapter keeps cylinder thread from wearing out
            • It's OK to use CHT gasket probes
            • The adapter is made from aviation grade aluminium bronze, no temperature stress to the cylinder head
            • Installation is reversible, you can always switch back to aviation spark plugs if you wish
            • Replaces both REM and RHM spark plug types
            • Very cheap to operate, even with Iridium type sparks: save money and get fast ROI!

Minor modification of HT wire required (reversible). 




Replacement spark plug type may vary from engine to engine, however NGK BR9ES might be a good start. 

You can go to BR8ES from there if it's fouling during normal operations, or to BR10ES if it's overheating. Or you may try several types and decide which one is the best for your engine.  

Please make sure you've got genuine NGK sparks, copies are much less reliable. 

Pictures are taken on my C172 with Continental O-300D engine, Slick mags.

I use these adapters myself for several years and so far have had no spark plug related issues with cold starts, misfire, lean operation, radio reception etc. 

Thanks for looking and happy flying! 


Please note this adapter is not certified by the FAA. Sending adapters only, copper washers are not included ($0.95 at Aircraf Spruce)