What could cause this?

[Wood Doctor]

Seems like the skirt could rock on either the intake or the exhaust port. In my case, the piston skirt's exhaust side was broken apart and the case was chipped off along with it. I suppose once the skirt broke apart, that piece could have taken out the case as it flew around for awhile.

 

[trooney]

Some more pics, there goes the AM theory

 

[trooney]

 

[trooney]

I guess it was an 034 piston, the ipl has an asterisk beside a 46x1.5 piston ring. Maybe an old one

 

[Redfin]

Those skirts do not look to terribly thin Tom. Have the intake pic?

 

[Deets066]

Could have cracked it from clamping when the pop up was cut. How much run time after porting?

 

[Motorhead]

Check the carburetor to make sure the screws are still in the butterfly’s

 

[trooney]

Could have cracked it from clamping when the pop up was cut. How much run time after porting?

Not even 1/2 tank.

Those skirts do not look to terribly thin Tom. Have the intake pic?

No, I forgot. Been sick as *s-word here lately. I'll get em for you hopefully tonite.

 

[Deets066]

Not even 1/2 tank.
.

 

[srcarr52]

View attachment 139739 View attachment 139740

That piston should have been replaced during the rebuild.

There is not a machine mark left on that skirt. You can barely see the faint remnants of machine marks near the ring lands. In my experience when the machine marks are warn off that far up on the skirt the bottom is 0.003-0.004" small which would pretty much triple the stock piston to cylinder clearance on 46mm bore.

 

[trooney]

Yeah, I think I will put it back to stock and sell it. I'll hold on to the jug. Its another JMS product that went bang!! Could've expected it though. So you think it was from fatigue that it gave way?

 

[trooney]

Or if I read your post correctly its from the piston rocking back and forth in the bore as I've been told before?

 

[srcarr52]

Or if I read your post correctly its from the piston rocking back and forth in the bore as I've been told before?

The more worn the piston the more it is allowed it to rock, eventually it will rock enough to snag the intake port or crack a skirt from impacting the cylinder wall as it's now bouncing around in there.

 

[Tractorsaw1]

I’m sure you probably sent a new piston & JMS swapped in a completely worn out piston most would throw away - JMS standard porting/operating procedure

 

[RI Chevy]

Figured it was good enough for who it was for. Justified his thievery in his head.

 

[maulhead]

Figured it was good enough for who it was for. Justified his thievery in his head.

Still have that ms440?

 

[RI Chevy]

440 was sold to a guy in MD before the SHTF with THAT GUY.
Lol

 

[maulhead]

Pour guy...

 

[RI Chevy]

I reached out to him several times to see how he liked it.
Haven't heard back from him.
He was like a 1 and done post guy. ‍[emoji851]

 

[Bigmac]

Some more pics, there goes the AM theory

View attachment 139736 View attachment 139737 View attachment 139738

That’s a lot of carbon build up for a half tank!