Hi all -

I have an ‘09 JCW with the N14 engine. Long story short, there are 8 bent valves. The guy who replaced the chain and guides reused the single use bolts and didn’t tighten down the cam sprocket enough. There are a couple nicks on each of the pistons (circled in image). Is that a problem? Should they be replaced?

 

Definitely not an expert here but at the absolute very least I would get some scotchbrite pads and "blend" out the raised metal in the top of the piston so it is smooth with the adjacent surfaces. Ridges and high spots like that can create hot spots in the metal which will lead to pre-detonation of the air/fuel charge (aka knock).

 

I used a Dremel grinder on mine, then re-balanced them. 'Course they weren't installed at the time and much easier to do without getting grindings between cylinder wall and piston. As said above --- somehow smooth them out to eliminate hot spots. If not a hi-performance engine, don't worry about re-balancing, just try to remove equal amounts from each piston.

 

Even though it’s a JCW, it’s a stock N14 engine - so we should be okay with knocking down those high spots?

 

Yes. By "hi-performance" I'm referring to at least double OEM HP.

 

He cleaned things up a bit and knocked off the burrs.