DarZeelon
The only aero engines, for which the A3 glow-plug is recommended are LA engines up to .40 and all up-to-.32 engines.
Hi Dar.
I checked the original OS site and the A3 is reccomended only:
<< For R/C Aircraft
Running-in, Engines smaller than .32 capacity
Engine types: 25SF, 25FX, 10-40LA>>