engine and drivetrain Damn! Scuffed Piston Skirts!

[roadhog0]

Ive been known to get em off with just propane and penetrating oil, but it's a lot slower process... Always worth a try.

[mike472]

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I've never "touched up" an engine like this; it's always been all or nothing. If nothing else, it'll give me the hands-on and gut-level experience to know never to do it again if it goes south on me.

"Too many negative waves Moriarty". Repeat after me..... It's not going to go south, It's not going to go south.....

[cda951]

His overall pronouncement is "if it were my car, I'd ball-hone it, re-ring it, put it back together, and drive it." He also recommends that I touch up the valves, even if it's just a light lapping. As much as I don't want to touch the head, I'm going to let myself get dragged down this part of the slippery slope, then dig in the ice axe and the crampons.

 

The new Deves rings just arrived. I'll test-fit the top ones in the grooves and check the side clearance. But I'm likely to follow Bruce's advice.

 

I've never "touched up" an engine like this; it's always been all or nothing. If nothing else, it'll give me the hands-on and gut-level experience to know never to do it again if it goes south on me.

 

Therein lies the beauty of a stout, old-school iron block design like the M10.

 

My shop works mostly on Porsches and newer BMWs. With aluminum engine blocks and Alusil and Nikasil coatings, the above is simply not an option in most cases if there is any amount of scuffing involved.

 

Almost any machine shop can overbore the cylinders of an M10 if need be. When the cylinder walls are worn or damaged in more modern AL open-deck blocks, only a few very specialized machine shops can reliably re-plate the cylinders and replicate the factory process. Sleeving an AL block also takes experience to get it right. In an air-cooled 911 the pistons and cylinders are easily replaced, but this is not cheap!

 

I would plan on revisiting this engine in a few years, as the piston ring to land clearance will eventually be an issue if one or more are at the outer limits of spec . . . . 

Edited March 2, 2014 by cda951