[Kitch428m21]

I've pulled the pan on 2 of the motors I have laying around just doing a general inspection.
On both of them, one a late 400, and the other a late 428, I've found a broken piece off the piston skirt. About a 1" sq piece. One on each.
What could be causing this? Is it common to find this in the bottom of the pan in Pontiac motors?
Nothing else is found coming apart and it's toward the back cylinders.

[BVR421]

I have found a piece from the very bottom of the piston shirt on a couple factory original motors, about as big as a fingernail
no idea if its common or why, I just figured they suffered from a lot of vibration from running cheap gas in a 10-1 motor and lots of detonation
lots of high CR 70s cars ended up in the wrecking yard after being abused as 'used cars/beaters' in the 80s, 90s

[Mr. P-Body]

John,

How ya doin?

We found the same thing when we openned up Joe's 428 ('69 Catalina wagpn, 360 HP). Detonation is the only logical explanation.

Jim

[Kitch428m21]

Jim! Doin' great! (both car and me)

Yeah, makes perfect sence what you both said. I happen to know this 428 took a beating with the 13 heads on it. (at times)
I figured I'd see a broken ring land or two and not the skirt.
Good news is the cross hatching on the std. cylinder walls is still plainly visible and no scars.

[taff2]

I used cast pistons in one of my early turbo engines,and after a spate of detonation I found quite a few pieces of piston skirt in the oilpan.

[torqjunki]

I had a motor that did that from the windage tray coming apart.

[1971WARBIRD]

found an XF 1970 455 in a wrecking yard years ago that had several pistons that were broken like that.#64 heads so it had some compression,but what i think killed it was where they knureled the cast pistons.don't know why they did it,as everyone had either pieces broken off or were cracked.

bored it .030 and ran the daylights out of it till i sold the car,best running engine i ever had.

[4SLASH6]

had a .060 over 389 with some forged trw's . was high compression motor. found I broke # 8 skirt pretty bad when I took it apart. broke #8 piston on a 67 olds 400 also.