I'm running an OS EB Mods V-Spec .21 in my 8IGHT. I've got about 3/4 gallon through it. So far every race day, I've gone through a P3 (the plugs EB says to run in the engine) plug. And they're not burning up. The elements are breaking. Twice I've had them break in the middle of a main where the car will stall, then when it won't start again, we pull the plug out and the element is broken. Every other time, it's after the main, I go to put after run oil in and check the plug and it's broken. The engine runs great, but what's the deal? I'm still not really clear on the different plugs. Is a higher number hotter or colder? Would you run a colder plug in hot humid weather? etc... It's been really hot and humid around here lately (100º+ and very humid) so I don't know if the P3 is too hot of a plug for that kind of weather or what. I was running O'Donnell 30% and I've started running Nitrotane 30% and it's done it with both fuels. I've got a bunch of Orion Turbo 6 plugs that I could use. I ran one in a qualifier and not having time to tune the needles, it ran like crap. Would that be a better plug? Is it a hotter or colder plug.

Sorry for the rookie questions. Still trying to wrap my head around tuning nitro engines.

.21's generlly eat more plugs then .12's. If the element is breaking, it's usually from pre-detonation or excessive compression. also, p3 sounds very hot for a 21. they usually use much colder plugs. try an os 8 and see if that helps........

Jon,

The P3 is the hottest plug in the range. You might try a P4 or a P6 for hotter weather. Check the top of the piston and the head button, is there any pitting? Pre-detonation will kill plugs like you're describing. The plug wire will also be gray and pitted as well. Check those things first and then go from there. I have other things you can check but it's more involved. You can PM me if the first suggestions don't work out.

Socko

Since you're running 30% nitro and using it in a .21 motor... You should really be using only a warm plug on cold days and a cold plug during the Summer months... Switch to a OS P8 and re-tune your motor... You should be fine after that... If the weather in your area is a bit cold, then drop in a OS P7... You should only need to run a hot plug if your running 16% nitro or lower. P3 and P6's are hot plugs and are used mostly in small block .12's...

RC_Alan

jon here is a chart and description of different plugs http://www.outlawrc.com/glowplugs.htm

Thanks guys. One more question. When I go to a #8 and I'll need to re-tune, which way should I need to adjust. Leaner or fatter?

your head shimms should add up to 0.6 mm for 30% even 0.7

Jon,

You've got PM.

Socko.

Back at ya. Thanks.