74 power wagon dream truck...

318willrun said

Usually with detonation, the spark plug insulator will generally have "metallic" looking specs on it. Detonation will cause the ring to overheat, and it can freeze up in the landing. Piston will show as well. Detonation is like most things, mild to wild. Just want to make sure you don't miss the mild symptom or it can go wild .... LOL

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I've seen the signs of detonation on my duster when I took these heads off of it the first time to have the 202 valves put in them. There was kind of a blistering in the carbon on the tops of the Pistons. I have none of that here... And I swear not even my duster with flat top pistons have this much compression but then again I had a much more radical cam in the duster at that time...
I think it's just a lot of cracking compression and not a good performance gasket...