Ding in piston rim

[jaybird840]

I am about to mate the pistons with the cylinders, and discover this...




I don't know if it was carelessness on behalf of the machine shop when they cleaned them, or I was careless with storage. Either way, I am where I am. I would assume this nick would score the cylinder wall? What is the best way to address it? My thought would be to dress it down flush with a fine swiss file. What say the masters? Onward with the rebuild....

--Jaybird

[silver911rdb]

I would use a machinist stone or similar. Lightly stone it down so that it's flush with the surrounding material. Obviously only stone the affected area.

Anyhow that's what I would do. I'm not a master builder but i have built a few 911 engines and have come across that same situation.

Good luck with the build!

[911pcars]

The only negative impact this would have on the piston is if it affects the piston ring groove dimension. Run a new ring in the groove and see if binds at that location. If not, carefully remove any high spots caused by the dent. Also remove any sharp edges caused by the dent or your repair.

Sherwood

[Mo_Gearhead]

As suggested, dress/smooth it down.

Sharp edges on a HOT piston dome can cause a 'hot spot' that can pre-ignite the mixture at the wrong time, causing detonation.

We always smoothed the sharp edges on high compression pistons, where the valve pocket was cut, just to be safe.