piston damage

What would cause piston damage like this? Case VAC number 4 piston, camshaft side of piston. None of the others are damaged just normal wear. Conformatic GE 130 pistons. Sleeve just has light visible scuffing. No knocking or rattle from engine. Rod bearings are within spec when checked with plastigage, I'm going to check crank with micrometer. Wrist pin bushing DO have excessive wear. Would worn wrist pin bushings cause this damage?
<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto114345.jpg>

<img src=https://www.yesterdaystractors.com/cvphotos/cvphoto114346.jpg>





This post was edited by J Hamilton on 01/16/2022 at 04:04 pm.

Bent rod, doesnt take much.

No visible difference when compared to the others, checked them on a flat surface with a straight edge. Is there a better method to check or measure them?

I had to rebuild my SO's 1984 CJ5 engine with about 40K miles on it. Started to rattle a bit. Found #6 piston skirt had broken off. Never off-roaded or abused. Probably manufacturing defect. When she sold it, there was about 300K on the clock. zuhnc

What was in the oil pan, one big piece, or small broken pieces?

Any damage to the top, like something hit one side and cocked it sideways?

Hard to say, possibly it was defective from the beginning, or damaged during assembly, possibly dropped.

Seen modern automotive pistons crack from excess skirt clearance, but unusual on the old style full skirt type.

One large piece and several small ones, no damage to top

it must have had a cracked skirt. also a rod resizing machine will tell the story on the rod
.

Yes a good machine shop will have a fixture for this purpose. See video. Notice that opposite end of the fixture had a larger holder for bigger rods. I would personally say there was a manufacturing flaw in the piston that just decided to fail. Shauns theory may also have some merit.
Checking a rod for straightness

Thanks guys. I do have a good local machine shop, I'll take them by there to have them checked

that video is not much... if the wristpin bushings are loose pretty hard to find a straight rod that way! as i said the sun resizing machine will tell u pretty quick. plus as you said if the bearing are worn even across the rod cant be at fault. has to be the piston. if the major thrust side has a crack along with excessive clearance that will be the out come.

Agree. Likely a factory defect. Interesting. Jim

Was the damage on the piston on the Major Thrust side of the piston ?? or the Minor Thrust side of the piston ??
Bob..

(quoted from post at 09:28:22 01/17/22) that video is not much... if the wristpin bushings are loose pretty hard to find a straight rod that way! as i said the sun resizing machine will tell u pretty quick. plus as you said if the bearing are worn even across the rod cant be at fault. has to be the piston. if the major thrust side has a crack along with excessive clearance that will be the out come.

Click to expand...

You must mean the manufacturer Sunnen, ran one of their connecting rod resizing hones at the Auto, Truck and Machine Shop I worked at in the early 80s. It did not have any way to check the straightness of the rod that is not its purpose, see video in link. Thus we had a fixture very similar to the one shown in the video in my other reply. You would remove the piston from the rod and give an initial check for extreme bending. If the pin was loose you found a proper feeler gauge to hold the pin tight. If that checked good you would grind down the big end cap mating surfaces with a special grinder also built by Sunnen. Torque the rod bolts up in the special rod vise that assured the caps aligned properly then you would run them on the hone as shown checking them periodically for size on the gauging fixture. Then you would fit new bushings in the small end and resize that end to fit the pin. After that the final straighten check was made with a tight fit pin. The Oliver White Waukesha rods were the most rubberish rods that would bend the easiest. And we also had a one piece replacement bushing for the two piece original bushings that were always pounding out. FYI ..Sun.. is a manufacturer of Automotive test equipment ..back in the day they made distributor test machines and oscilloscopes.. they are now a division of Snap-on Tools.

https://m.youtube.com/watch?v=5yqsEs8GG0Q

Edit to fix link.

This post was edited by used red MN on 01/16/2022 at 10:38 pm.

Looking from front of engine (fan side) the damage is like the pic on the left you posted

I would say possibly a bend rod way out of wack or maybe it even struck the crank.New one to me.

vac's are a dime dozen put it in the fence row and go buy one cheaper than you can fix that one

I'll give a dime for a dozen of them! And who's to say buying another one wouldn't need a rebuild as well or have worse problems?