Originally Posted by articfriends (Post 4886726)

https://cimg8.ibsrv.net/gimg/www.off...3b8089d2df.jpg
https://cimg9.ibsrv.net/gimg/www.off...930da68a85.jpg
here's 16 pistons I took out of recent 540 rebuilds, they were slapping ike a screen door in a hurricane im.sure! I never did identify wtf they are but tiny skirts, short pins, super lighweight.

Originally Posted by articfriends (Post 4886726)

here's 16 pistons I took out of recent 540 rebuilds, they were slapping like a screen door in a hurricane im.sure! I never did identify wtf they are but tiny skirts, short pins, super lightweight.

Originally Posted by BillK (Post 4886756)

Whats interesting on those is that the bottom of the skirt looks fine ? I would think that if they were loose and rocking that the bottom of the skirt would take the most beating ? Strange.

Originally Posted by Twin O/B Sonic (Post 4886626)

I have noticed the very short skirts lately too.

Mostly in car drag apps, and when I see them in the Offshore market I always wonder.

In the photo above, of the one w/the worn skirts, there is near no skirt bellow the bottom of the wrist pin!

All the skirt support is above the pin and that is where there is already increased clearance designed in for thermal expansion.

Add to this the variable of combust chamber design, piston dome design and plug location.

As in, how much of the combustion process is actually side loading the piston from the start?

And w/little to no skirt support bellow the pin to counter the above…….

The short skirts would make me nervous, especially in highly loaded, high torque scenarios.

I bet there is an Engine Masters episode on this????

If not, should be.

Originally Posted by BillK (Post 4886756)

Whats interesting on those is that the bottom of the skirt looks fine ? I would think that if they were loose and rocking that the bottom of the skirt would take the most beating ? Strange.

Originally Posted by articfriends (Post 4886757)

This was a more convoluted story, these had the coating from factory stripped off and were RECOATED very poorly by a engine shop in Virginia. They were also then put in a block at about .008 to .010 along with bad machine work and assembly. The coating came off of them and went thru the oil system nearest I could tell as both cranks were torched too.

Originally Posted by BillK (Post 4886806)

That makes more sense. Personally I am not a fan of having pistons coated to tighten up clearances. I know quite a few shops swear by it but I feel it is just a bandaid. If the pistons are that loose you either need new pistons or the block needs boring or both.