Cox engines FAQ's

What do cox engines run on?

They run on glowfuel (nitromethane castor oil an methanol)

Can they run on other fuel?

They can be converted to run on model diesel fuel and one can make other improvised fuels but this is not recommended.

How does one Fill te tank on a tanked engine?

There are two holes one is a vent either can be filled you know it is full when the fuel starts over flowing from the other hole.

How does one start their engine?

This depends on what engine you have

For reed valve engine: fill up the tank,turns the prop over a few times to prime the engine, then attach the glow igniter to the glow head, squirt a few drops of fuel into the exhaust ports then if your engine has a spring starter engage it and spin the prop round 1/2a turn clockwise if your engine is a puller or the opposite way if it is a pusher.
If the engine does not have a spring starter flick the propeller anti-clockwise to start it. Or vis-versa if you engine is a pusher.


If you have a front rotor engine then the instructions are exactly the same apart from the priming procedure. To prime the engine place your finger over the venturi and take the engine through compression until rounder fuel go to the venturi from the tank. Note this will only work if you needle valve is open.

Do these engine need castor oil?
Yes absolutely they need at least 10% castor oil some synthetic can be in there as well but the total oil content of the fuel must be at least 20%.


Do the engines need a high nitro content?
It is recommended but not essntial some have run their engines with no nitro in the fuel but to make adjusting the needle valve easier it is recommended to have at least 15% nitro.

What fuel blend do i recommend?
Something with 25% nitro and 20% all castor oil rest is methanol.
That usually means sig champion 25 throughout north and south America or Model Technics GN 25 in the UK.

What is the reccomended needle valve setting?
Each engine is different so settings vary but 4 turns out is usually a good place to start at. Then work your way in or out.

How do I know if my engine is rich or lean?
If the engine splutters and spurts out fuel from the exhaust ports it is too rich you must turn the needle valve in.
If the engine starts up with a lot of power then dies or becomes extremely hot turn the needle valve out.

How do I find a good setting to run the engine once it is run in?
Get the engine to run as lean as possible then from there open up the needle valve 1/2 a turn.

How do i run in my engine?
Simply let the engine run rich for a while different people do this for different amounts of time I believe 1/2 an hour Is good but 45 mins is better.

Do I need to wear ear protection?
It is up to you I really do not believe it to be necessary but if you are running your engines for a long period of time often then you might want to, I do when I am running engines for more than an half an hour.

Is more power gained from a diesel conversion?
Yes more power is available as a diesel and the engine Is also more efficient but diesels prefer to spin larger props. Some engines will fail prematurely as diesels it is usualy the crank that breaks first.
More info to be added soon.
i'm off to see the Eifel tower.
Hope that helps someone