Something In my #5 Cylinder?

Walker434 said

Thanks for the reply guys. Bore scoped again last night and found a chunk of #5 piston is gone. See picture below. Well, regardless of what happened I'm pulling the engine this weekend. I did Drag Week this year with this new combo. I think I was running too much timing and got into some detonation. Backed the timing way off and now had the tune just right but I think the damage was already done.

Boost learning curve I guess. I'll inspect all pistons and bearings but maybe I'll get lucky and only need to replace #5 piston rings and bearings? We'll see. Hopefully the head isn't also hurt.

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Glad you found that, but to me, that doesn't explain the plug getting closed up.

It's hard to tell from a picture but from what I see that doesn't really look like a detonation issue. Usually detonation looks a lot more ragged. I suppose if you had enough time on it after the failure, the heat from combustion could have smoother it out some. And the piston is usually pretty thin there so if it was detonation, you may want to get your piston guy to drop the rings another .100 so the tune up isn't quite so sensitive.

I'd rather lower the rings and get the tune up window wider than keep the rings up so high a small tuning error will eat parts.