random thought

[yankeeone]

My buddy came over to look at my r80 rt , and asked why the bottom of the piston-- cylinders don't wear out from the weight of the piston, and rods pushing down in the horizontal configuration . Any thought's?

[Ken F]

When the engine is running there are lots of forces working on the piston other than gravity, keeping it centered.

Porsche, Volkswagen, Subaru, Citroen, and many others have been sucessfully making "boxer" engines for many years with no adverse wear patterns.

Hope that helps....
460

[crazydrummerdude]

I wonder in which direction they wallow out..

[Jeff488]

IIRC, my '65 beetle's pistons had slightly offset wrist pins. There was an arrow cast into the underside of the piston to show which side should be "up".
If one didn't know about this and got one of them wrong way to, it caused noticeable piston slap. DAHIKT
Makes for good practice in engine removal and disasssembly/reassembly.:banghead

Apparently it's not the same for Beemers.

[beemerguru]

Oh but it is...there's an arrow on top of each BMW piston and the rods only go in a certain orientation

[36654]

My buddy came over to look at my r80 rt , and asked why the bottom of the piston-- cylinders don't wear out from the weight of the piston, and rods pushing down in the horizontal configuration . Any thought's?

1) The weight of the piston and connecting rod is not significant relative to the pressure loads

2) The Piston rings and skirt act as rudimentary fluid film bearings which center and stabilize the piston. If the rings wear or have a loose fit, you'll get piston rattle in any cylinder configuration. Two years ago, Subaru rebuilt one side of the engine on my wife's out-of-warranty car. Either the piston or the rings were undersized by design, resulting in piston rattle and, eventually, head gasket failure