ORIGINAL: earlwb

You don't have any local hobby shops? It seems like there ought to be quite a few hobby shops in Egypt.


Just for your general information.

There are basically three heat ranges of glow plugs, a hot, medium and a cold plug. Some brands might have a few more heat ranges in between. Most engines for sport useage only need the medium heat range glow plug. A cold plug would tend to be for high rpm racing applications, and a hot plug maybe for engines that have a need for it due to lower rpms or power strokes or compression ratios, such as the 4 cycle engines.

Now the short reach versus long reach glow plugs, if the engine is a .25 (or 3.5cc) size or smaller in displacement, it uses a short reach plug.
Some newer bored out .25's like the .32's and .36's use a short reach plug too. But old style large crankcase engines like the .29's and .35's use the long reach plug. All engines 40 and above use the long reach glow plug.
Some old antique engines with dual plugs may run both, one short reach and one long reach glow plug.

Now then there are some special glow plugs made just for 4 cycle engines. These have a machined shoulder or step at the bottom of the glow plug to fit a special recessed part in the glow plug hole on the engine. OS is normally the engine design that uses this special shaped glow plug. A regular long glow plug will bottom out instead of threading all the way down. As OS didn't drill and tap the glow plug hole all the way through the head.