Why? (Blowing plugs)
 

I was wondering if anyone could shed some light on why you would blow a glow plug. I was running in a race and the glow plug just blew it would start up but as soon as you took of the glow plug the engine stalled. This happened 2 times on in a qualifier and the other in a main.
I am running an RB WS72 Motor and the engine temp was 235-240
I was running a McCoy plug #8 I beleive medium plug.
Any info would be appreciated.

There could be a lot of things but most of the time it's caused by being too lean on the bottom end. When you let off throttle abruptly the cold air charge hits the plug with no or very little fuel which causes an extreme lean condition. That is what usually smokes the plug. What does it look like? Does it look like it got "white" hot or is it melted? What fuel are you running? What are the "other" guys using for plugs that are running your fuel?

Other things like small air leaks in the motor can cause a similiar effect as well. Basically, you are pinging on the low end but when you crack open the throttle your out of your low end adjustment and into your main at that point...

Hope this helps...

Like Randy Pike said, it could be a lot of things.

Most likely it is when the engine is rich, and the plug is not able to ignite the extra fuel in the combustion chamber...so your engine flames out.

You either need to lean it out with proper tuning, or buy a hotter plug for that engine.

Bob
if the engine is developing plug contamination this will occur. The engine runs with the glow lighter attached and stalls abruptly when you take the ignitor off the engine.(yes assuming its properly tuned) Look at the first coil of wire where it is welded to the plug body. Look to see if it has developed black death, (the first 1 mm of the wire is black. If so or the plug shows any signs of a dull grey buildup you need to find the source of contamination) It could be bad fuel. (it happens alot) a tear in the air filter so dirt is entering some way or a rod bushing that is going south. Also you have not used any silicone that was not oxygen sensor safe anywhere on the engine have you? Straight silicon will contaminate the plug and coat the platinum element and it will stall and foul plugs quite a bit. Never use any silicon spray either anywhere around your engine or inside of it. Since you indicated it restarts and stalls your mixture can't be that far off as it is not totaling the wire element out.
Dennis Richey
AKA Motorman

As far as fuel I am using Sidewinder 30%.
The plug blew once at the middle of the straight and the other time coming out of a corner.
I have not used any kind of silicone to seal the engine.
The plug coil looks greyish. I do not see any black on the first part of the coil.
I have been running 10th scale gas truck for around 4 years just moved into 8th scale and I never came across a problem like this.
I feel that I can tune and engine farely well.
Hope this info helps out.
Thanks for the advice.

You should also be using a colder plug when running 30%. The same thing happened to me this weekend, embarrasing.

well...the rear bearing in my engine went and was throwing little pieces of the bearing into the plug....blew every other run....replaced bearing, plugs last 1/2 gallon.

Bob try a new gallon of fuel. Most likley its a fuel issue.

Aye...back when I used to run Sidewinder, the quality would change dramatically from gallon to gallon. I would have to use different plugs and tune my engine differently to compensate for the slight changes.

Try some good ol' goat piss, or better known as Byron's... :nod: