need help understanding short standard glow plugs

[mattvictor]

I race 1/8 scale off road buggy. I have been out of the game for a couple years .my current engine is a pico evo 2 . I purchased some o s plugs from hobby town ,and they have short bodies on them making an odd combustion chamber . can someone give me a detailed explanation of these short bodied standard glow plugs and why they are used . also will this be detrimental to me and my engine ?

 

[w bill]

The lenght depends on the engine design as far as what it takes.If your thinking a standard plug with out the idle bar that design has become basicly obsolete.That would be the correct plug for your engine.The only time you would have a problem would be using a long in the wrong app then you could punch a hole in your piston even if it turned over.

 

[mattvictor]

Thanks for the reply, but I don't know what an idlers bar is. I just used to use os plugs, and have the standard head picco evo 2. So I'm using a short plug, an os 7, which hobbytown said was fine. But an experienced co-racer told me that the small space of exposed head button threads could produce a poor action, and create a "hotspot" up there. Others tell me its not a problem. Keep in mind too...I'm in Colorado at high elevation. I'm just so confused now.

 

[w bill]

Thanks for the reply, but I don't know what an idlers bar is. I just used to use os plugs, and have the standard head picco evo 2. So I'm using a short plug, an os 7, which hobbytown said was fine. But an experienced co-racer told me that the small space of exposed head button threads could produce a poor action, and create a "hotspot" up there. Others tell me its not a problem. Keep in mind too...I'm in Colorado at high elevation. I'm just so confused now.

That little bit of exposed thread won't hurt anything as far as altitude just tune accordingly.The idle bar used to be a small piece of metal that went across the coil of the plug so at idle the fuel would not foul the plug.

 

[mattvictor]

so I went out and practice with the short bodied o s number 6 and number 7 plugs ,and my pico ran well. then I put in a purple top o donnell with a standard length body and my motor ran like poop . is it the plug or is it my tune. some people said at hobbytown that the purple top would be fine ,others said it's not a race plug more of a play plug ,do I just need to read soon my motor to that plug with significant changes ? I'm also a little paranoid that I got dirt in my motor changing the plug trackside ,but I'm usually an anxiety case . Lol. any words of wisdom ?

 

[2revo1maxx]

Use an O'donnell #99 plug. It's a long type, medium heat, and will rock that engine. Forget those color top O'donnell plugs they suck.

 

[w bill]

OS#8 would also be another good choice for a plug.

 

[2revo1maxx]

Nothing wrong with the #8 either, except they're short.

BTW there are 2 #99 plugs, turbo and regular.

 

[mattvictor]

do those purple plugs really suck ? by the way the o'donnell 99 doesn't work up at high altitude very well . anyway is it just that I have to re-tune using the purple head, because how could a plug suck ? especially made by o'donnell .yes right before I put it in I used a short body number 6 and 7 and they were working fine . I just bought that o'donnell purple head because it was on sale at hobby town and I wanted a long body plug 4 a nice smooth half circle combustion chamber . but then it got all hard to tune. it wouldnt idol right it wouldn't stay running ,so I thought it was a matter of tuning for that plug .so I have the other ones I even have a mccoy number 8 for the long body,it just got dark out before I could test it and I was getting frustrated with the purple head o'donnell . so should I just work on tuning to the purple head ,because I bought a few of them ,or are you saying just throw them out , I don't understand how old donnell could make a crappy plug . it lights up it makes my engine go it should be fine right ? and the purple was the 1 rated to using 30 percent fuel. could anyone explain how that plug could suck ? could I ever get it to tune and run right ,just because I'd hate to waste them .

 

[2revo1maxx]

I wouldn't throw them out, they're just a 'sport plug'. The 99 is a high performance big block plug. Whoever told you that plug won't work at 5000 feet is crazy. Do you have a carb insert?

 

[mattvictor]

yes I have all the inserts .what do you mean a sport plug ? I'm club racing right now with my ninja turbo head ,but I plan to test my picco afterwards and try the purple plug again .

 

[2revo1maxx]

What I mean is it's a cheap plug that you'd run in a traxxas 3.3 or something. The blue, purple, and red plugs are all 'sport plugs'. I'd try any other O'donnell plug that is medium heat.