Model Engine Company of America

How do they work...

Glow plugs work because of a catalytic reaction between the methanol based fuel and the platinum element. Without this fuel or the platinum wire the glow plug would not continue to glow when the 1 1/2 volt booster battery is removed. See also Fuels and Compression Ratio

The torque to tighten Glow Plugs should be 20 to 24 inch pounds. Just snug, the copper gasket does not require much pressure to seal, and a turbo type plug seals with little force also.

Volts to light a glow plug is 1.2 ~ 1.5

When the battery is attached the element should glow a bright orange. Bright enough to make spots in your eyes.

Different Heat Ranges

More info below

Glow plugs come in different heat ranges with different mixes of platinum alloys and different size wire. The alloy used is considered a trade secret and it is doubtful any manufacturer will disclose the actual alloys.

Some plugs have nickel plated bodies, some have black oxide finish. Some even gold plating. Believe it or not these finishes also affect the running characteristics of the glow plug.

Different Sizes and Types

The thread size is a standard 1/4 x 32 UNEF since prior to its invention in the 1940's. This is a carry over from the spark ignition engines of that time. Some engines back then did have 3/8 x 24 thread plug and some glow plugs were made in this size but I don't think any were made since the early 1950's..

There were for many years the thread length, or reach of the plug was just short and long. Now there are what we consider a medium reach, like our new K&B Detonator Plug used on most car engines. Check your engine specs to be sure which one to use. Most common is the long reach.

There is also what is called a turbo plug. This plug uses an 8mm thread and seals with a tapered seat at the nose of the plug. This is done because it creates a smoother combustion chamber thus producing better performance.

.156" 5/32" thread length for the Short reach -- Not Common used mostly on engines under .21
.177" 4.5mm thread length for the Medium reach --
Not Common used mostly on car engines under .21
.218" 7/32" thread length for the Long reach --
Most Common used on 96% of engines

What glow plug should I use for aircraft engines? For regular use in engines equipped with mufflers a standard K&B 1L  #7311 plug is good. In older engines a R/C K&B 4520 plug may produce a better idle. If you have trouble with short plug life a K&B 7310 heavy duty plug may be the best.

What glow plug should I use for Glow Plug Adapters?

The small 1/2A engines like a HOT plug like a standard K&B 1L  #7311 plug for a long reach adapter or
a K&B 1S #7321 for a short reach adapter.

What glow plug should I use for marine engines? If you are using less than 25% Nitro content fuel a standard K&B 1L  #7311 plug is good.  For 25% and higher content Nitro fuel a K&B 7300 high performance plug is recommended. Note: Early K&B 3.5 outboard and marine engines used short reach plugs and later changed to long reach. Plug thread should not extend past the threads inside the head combustion chamber.

What glow plug should I use for auto engines? Check to see if your engine uses a long or short plug. We recommend a K&B 1L #7311 long or a K&B 1S #7321 short

What glow plug should I use in 4 stroke engines The K&B 4444 plugs work perfect in all poppet valve four stroke engines.

What glow plug should I use in HP VT 4 stroke engines The K&B 7311 works perfect in HP VT four stroke engines. Don't use an R/C, 4 cycle, miracle or any other plugs that have anything extending from the end. These plugs can hit and destroy the rotary valve. Note: Early VT 21's use a standard short plug like the K&B 1S 7321. Look into any port on the head and you can identify the early version by the rotating valve, early used a bronze valve in a chromed sleeve, all later engines used a chrome valve in a bronze sleeve.
The above information is provided as a guide. Since MECOA/K&B has no way of determining the ability of the individual using and understanding this information, we assume absolutely NO RESPONSIBILITY for any damage to person or property from the use of this information.