Animal stroker egt

Just curious because we were at a winter indoor race where the temp was low 40's at best. Animal with a Mikuni and a China bomb on alky too. Both barely showed over 200 degrees CHT but both ran exceptionally well. Spark plugs afterwards both looked really good. What are your plugs telling you?
 
What do you think caused this?
Detonation.jpg
 
It's hard to tell from a pasture but if you look very carefully at the center electrode there are parts missing.
If you look at the side electrode that's where it went. It melted off the center electrode and then stuck to the cooler ground electrode.
Also notice 2 dark spots on the white portion of the insulator below and to the right. That's more melted metal deposited on the white insulator.
It had 38 degrees of ignition timing.
 
Jimbo said:
It's hard to tell from a pasture but if you look very carefully at the center electrode there are parts missing.
If you look at the side electrode that's where it went. It melted off the center electrode and then stuck to the cooler ground electrode.
Also notice 2 dark spots on the white portion of the insulator below and to the right. That's more melted metal deposited on the white insulator.
It had 38 degrees of ignition timing.
Click to expand...
I see it now. Little chunk missing from the center electrode. Did it melt the piston too, Jimbo? You would think it would liquify the aluminum long before the center electrode, but either way that dude was seeing some pretty extreme combustion chamber temps and pre-ignition and/or detonation. I'm guessing the damage was done pretty quickly where the cht would not have been of much use. Good application for egt on these engines for sure.
 
Jimbo said:
It's hard to tell from a pasture but if you look very carefully at the center electrode there are parts missing.
If you look at the side electrode that's where it went. It melted off the center electrode and then stuck to the cooler ground electrode.
Also notice 2 dark spots on the white portion of the insulator below and to the right. That's more melted metal deposited on the white insulator.
It had 38 degrees of ignition
Click to expand...
Ive melted a few piston in my time.
 
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