In my experience the .049 engines that were not made with a glow head like Cox used short reach open face glow plugs. The long reach plugs can be used with extra washers under them. Do not even try an idle bar plug. Try a Fox Short Standard plug. Also remember some of the older engines were not power houses like we have today. If they turned 8 to 9 thousand RPM it was great. Also what fuel are you using as 10% nitro is not enough for top performance. Later, DOC Holliday