14mm plugs with adapters
Denso L14-U are excellent and are what I'm using. I know people who have run them for decades with 1000's of trouble free hours replacing them annually.
Honestly don't know why anyone would monkey around with the adapters.
Hi Brian, emagair recommends plugs in this heat range:
- NGK BR8ES
- NGK BR8EIX Iridium Electrode
- Denso IKH27 (for long-reach heads with LR adapters only.)
These are 14mm plugs that need the 14mm to 18mm adapter.
The L14-U would be in the heat range of an NGK 6, so somewhat hotter.
I know with my two-cycle motorcycle engines going from an 8 to a 6 would have given me a nice hole in the piston in about 3 minutes, but it seems aircraft engines are not quite as sensitive to spark plug heat range.
Reading various things on the Denso site, it seems that there are two extremes when choosing the right plug - is it hot enough to burn off deposits? is it cold enough to avoid detonation?
It seems as long as the plug is between these two extremes, it's ok.
I just bought a batch of IK27 plugs and will run them for a while to see if I have any issues with deposits or fouling. The BR8ES plugs seem to be fine as well, but I like the fact that the IK27 are iridium, and they have solid terminals. They may be too cold, however. The IK27 plugs do look nice, and use a smaller socket, which is slightly helpful on the top of the cylinder where space is a bit limited due to the baffles.
These are 14mm plugs that need the 14mm to 18mm adapter.