ORIGINAL: bruce88123
ORIGINAL: armody
Hi there all,
I was just wondering that there are assorted glo plugs available, some have long heads, some have short heads, some have open filaments, some have a metal strip on the top of filament crossing from one end to another. My question is, if a gloplug has long head does it make any difference in any engine or short head one would work better? Gloplugs can be used for any engine either 2 stroke or 4 stroke and whatever the engine displacements are? or recommended or some particular gloplugs should be used.
Thanks
Mody
"long" plugs have longer threaded portions and if used where a "short" plug is required COULD actually hit the piston. If a "short" is used where a "long" is required it may not get down into the combustion area. The "strip" accross the plug is called an "idle bar" and is used to keep cold fuel from splashing on the element and cooling it too much and making it stop firing the mixture.
Always use the proper length as recommended by the manufacturer. The use if an idle bar is kind of option al in most modern engines although they are use more often in side mounted or inverted engines.
Bruce's advice is, as always, right on the money.
Just for a point of reference, short plugs are generally only recommended on engines smaller than .25 cu in in displacement. A short plug will be marketed as "short" whereas "standard" or "long" are normally the same thing, and if a glow plug only has it's heat characteristic listed and not length, it's usually safe to assume it's a standard long plug (Tower Hobbies Medium Sport Plug, e.g.).
Short plugs get used more frequently for car/truck glow engines rather than aircraft, but there are plenty of .10 and .15 sized glow engines on the market for aircraft that may use short plugs.