I heard a not so good noise just driving in town. I was only 4 blocks from home so drove on home, put it in the garage and shut it off. Finally got the time to tear into it (a little over a year later) and this is what I found. I'm not really sure what would cause this. I rebuilt this engine back in 1998, so I guess I can't complain too much. Just curious if anyone has seen this happen before and what might have caused it.

Thanks.

Click to view attachment

Any slack or wobble at that wrist pin? I've destroyed the top of one but never the side of one. Was there any piston slap before hand?

I haven't checked for slop on the wrist pin yet, but didn't notice any piston slap before hand. No real warning signs of any kind....running fine, then just broke.

Looks like it separated at the oil ring landing. Jake will have the definitive answer if he sees this.

I am wondering if piston defect. Weird break.

I had a Type 1 bug cylinder break in the up and down orientation. It was one of the cylinders next to the flywheel. The other side was cracked but had not broken yet. I figured that end had extra vibration.

As we dug into the engine on that car, we found out that a PO had used JC Whitney parts, or maybe the whole engine, I can't remember all the details back that far. So in 1982 we chalked that one up to lower quality parts. I haven't bought anything critical from JC Whit. since.

it may just be the angle you took the pic, but did you leave the rd bushing out ? That wrist pin looks WAAYYYYY off center of the rod end.

I wonder about overheat and collapsed the skirt till it broke off. If you look at the crown of the piston at about 1 o'clock it looks like scuffing or metal movement. I think I would check my temps/ cooling system when it went back together. Gordon

Check the piston to wall on the other cyls.

Looks fine to me. The pin floats in the wristpin bushing, and it looks square in the rod.

The Cap'n

Thanks for all the suggestions and observation. I will definitely take them all into consideration when I continue this rebuild. I am also concerned the it got too hot, but have not found anything wrong with the cooling system...ie. blower, oil cooler, and cooling fins all look good. oil was full and clean. Could the oil pump have failed?

If the oil pump had failed, you would have destroyed a rod or main bearing before the piston skirt failed like this.

Thanks ClayPerrine, I did some resource after I posted that and realized exactly what you said. So, does the oil pump push oil through the oil cooler also, or how does that work?

Oil pump feeds all the galleries which feed the rotating/reciprocating parts (mains, rods, valves, cam, etc. It also pushes oil thru the cooler and filter.

Air flow through the cooler is something else. If your thermostat is working that control the flaps in the blower housing, the cooler is bypassed when the engine is cold.

Thanks Slits. I'll check thermostat and flaps with a heat gun before re-installation.