Husqvarna 4.2 glow engine
03-12-2013, 07:30 AM
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Husqvarna 4.2 glow engine
I've got a new never run Russ Stolts Challenge Tool Husqvarna 4.2 that is set up for glow or alcohol use. It has 2 glow plugs in the head and wondering if it should run on 5% or 10% glow fuel. Does you set the carb setting just like you would on a gas engine. I've never run an engine like this and need as much info I can before I try. Thanks, Paul
03-12-2013, 08:05 AM
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RE: Husqvarna 4.2 glow engine
That looks like a really neat engine there. Nice find.
Many years ago I used to convert trimmer and blower engines to glow RC engines. That was before we had big RC engines we could get. But at the time, the compression is a little on the low side, so I used a on board glow ignitor to help keep the glow plug heated up good. Usually the gas engines are running around a 7:1 to 8:1 compression ratio and glow engine are running a 10:1 to 12:1 compression ratios. Alcohol lets you use higher compression ratios. Thus I could use 5% to 10% glow fuel no problem. Anyway give it a go and see what happens. If it doesn't seem to be running correctly, try some higher nitro percentage fuel too. You can also try more hot glow plugs too. In hindsight, I think at the time when I made my glow plug adapters for the spark plug hole, I had the glow plugs sitting on top thus having a hole on the inside that also reduced the compression a little more and isolated the glow plug more from the combustion chamber. I think idelaly one wants the glow plug element down at the top of the combustion chamber.
I typically made an adapter and stuck on a glow engine carburetor. But since Walbro does have a alcohol carb you could try it. Usually the gas Walbro carb has its jets setup for the much more lean running gasoline wheras glow fuel is used at a more rich mixture level. Some guys would modify the jets on their Walbro carb, but I went for just using glow engine carbs instead.
Also with the glow engine conversion of a gas engine, you can mix your own fuel and go with a lower oil percentage in the fuel. Since the gas engines normally have needle bearings on the connecting rods. Having more methanol in the fuel can also help make the engines run much more nicely too.
Oh yeah, you only need to use one glow plug ignitor to start the engine up with. The other glow plug will heat up from the hot combustion gasses. I don't think one really needs dual glow plugs, but it is a nice touch and doesn't actually hurt anything.
Many years ago I used to convert trimmer and blower engines to glow RC engines. That was before we had big RC engines we could get. But at the time, the compression is a little on the low side, so I used a on board glow ignitor to help keep the glow plug heated up good. Usually the gas engines are running around a 7:1 to 8:1 compression ratio and glow engine are running a 10:1 to 12:1 compression ratios. Alcohol lets you use higher compression ratios. Thus I could use 5% to 10% glow fuel no problem. Anyway give it a go and see what happens. If it doesn't seem to be running correctly, try some higher nitro percentage fuel too. You can also try more hot glow plugs too. In hindsight, I think at the time when I made my glow plug adapters for the spark plug hole, I had the glow plugs sitting on top thus having a hole on the inside that also reduced the compression a little more and isolated the glow plug more from the combustion chamber. I think idelaly one wants the glow plug element down at the top of the combustion chamber.
I typically made an adapter and stuck on a glow engine carburetor. But since Walbro does have a alcohol carb you could try it. Usually the gas Walbro carb has its jets setup for the much more lean running gasoline wheras glow fuel is used at a more rich mixture level. Some guys would modify the jets on their Walbro carb, but I went for just using glow engine carbs instead.
Also with the glow engine conversion of a gas engine, you can mix your own fuel and go with a lower oil percentage in the fuel. Since the gas engines normally have needle bearings on the connecting rods. Having more methanol in the fuel can also help make the engines run much more nicely too.
Oh yeah, you only need to use one glow plug ignitor to start the engine up with. The other glow plug will heat up from the hot combustion gasses. I don't think one really needs dual glow plugs, but it is a nice touch and doesn't actually hurt anything.
03-12-2013, 08:31 AM
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RE: Husqvarna 4.2 glow engine
Run it on straight alky with 5% oil. No nitro unless your racing.
To convert to gas you would need an ignition and a new carb. Remove the glow adapter an run a regular spark plug, take the other glow plug and remove the element and use it to plug the hole.
To convert to gas you would need an ignition and a new carb. Remove the glow adapter an run a regular spark plug, take the other glow plug and remove the element and use it to plug the hole.
