Jim, Calvin thanks for the pics. Personally I'd prefer to see the plug tip exit closer to center chamber for reasons I've previously stated. I would assume the water box around the plug would make it difficult to change it much from where it is now. My gut says plug indexing might be helpful.
Yes this may never actually occur. I'm hoping it doesnt. But I felt it worth alerting others who may have been/be focusing more on port development 1st than the final chamber. I/we will have to trust the proffesionals opinion/testing on this.
My related experience(2 stroke, hemi chamber, centered plug, no valves, not plug placement related) with preignition, tells me live testing is going to show if what I suspect could/will occur or not.
Lots of factors involved. Having a hot spot ignite the mixture as the piston is in vicinity of BDC compression causes rapid failure. Compressing a burning mixture overcomes the piston's ability to draw heat away and will lead to a hole in the piston long before you can react to any sound.
You DONT hear a detonation rattle. It starts at/near bdc not rapid brief shock of detonation. You hear your motor stop at 8000, maybe bang at same time, maybe catch again with power just gone! Occurs faster than you can read the 1st two words of this sentance.
Been there, seen it, helped cure it, after collaborating with a pro who was seeing same intermittant issue on what turned out to coincidently be an identically modified "stock rules"combo. Our case we had exceeded a power level beyond anticipated ability/use in the design. Our conclusion...the heads couldnt pull the heat way from the plug and/or head fast enough(suspect both). We found an already existing cooling mod for another motor was adaptible and ultimately it worked.
Problem didnt occur every pass. (in fact had a "minor" occurance after a breif decell and return to throttle once)
Nailing down the cure for a nasty intermittant problem can be costly if not just time consuming. Testing was challenging. CHT gauge on the plug didnt react fast enough and yet read safe before/during/after. Plug inspection when there was no failure gave no evidence, no speckles, no melt, nice strap etc.. An inpection after a fail had a melted plug covered in sprayed aluminum. Adjacent plug just fine. Hole in center of piston and aluminum sprayed everywhere. EGT was found to spike simultaneouly at/with failure. Safe before failure. (EGT quick response probes early racepak monitor) Best clue was more often occurance one side than the other. Slight detune with thicker head gasket or rich tune allowed no occurance but counterproductive to having an edge on your competitor.
Again I truly hope this possible issue doesnt occur and bite anyone.
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