lst2inIraq

This is my first werks motor, had all .28 stock motors before this. I am running ODO 20% with mc-8 plugs JP-4 pipe, weather in hot and not humid.The first plug lasted through run in and let go, it was rich and the plug was dark brown (coil bent) I started to tune for performance but still alot of smoke, ran well and had good idle slightly low. 4 tanks around 230 plug let go same dark brown coil bent, do you think its rich oa the low and lean on hi? It has good top end botom not to bad eather, but I am to rich somewhare. I have some R5 cold and ODO 100 for now.

I have ODO 30%,ODO 99 plugs and Jp-3 on the way!

helibrian

As I'm sure you already know, a collapsed coil usually indicates a plug that is too hot, causing pre-ingnition. In your case though, if you're running an mc-8 (you could still go colder), and still have the same issue, the cause is more likely caused by high nitro content, or too much compression. Both would also cause pre-ignition. So, your options are, to continue running 10%, shim the head, or invest in a bunch of glow plugs. I think after while your engine will loosen up a bit and this problem will go away.
You might also try going a little colder or a different brand of plug.

Mc-9
O.S. R5
Rossi R4 or R5
Enya #6
O'Donnell Blue

All cold plugs.

Good luck.

(edit): ok after re-reading your post, I see you're already trying different plugs and I wasted 45 minutes typing the lower half of my post.

gubbs3

iTrader: (7)

Odd. I have run 30% with a MC-59 plug and it still lasted nearly a gallon of fuel without deforming the plug. I did start blowing plugs though after about 6 gallons of fuel when the rod or rear bearing was worn, but I didn't bother rebuilding. One thing I did notice is that every plug I pulled from the engine was always dark brown or almost black when the engine was running well. The engine got pretty poor mileage (6min) which might contribute to the blackening.

I would disassemble the motor and check the rear bearing. Make sure it is slop free. Bad bearings or worn rod are usually culprits behind blowing plugs.