Quote:
Originally Posted by m4ml
This actually looks like they are CNC machining the combustion chambers (which is consistent with lowering the compression ratio).
Porting and polishing is done inside the intake/exhaust runners. Some clean up is often done from the combustion chamber side, but this picture shows fresh metal in the first combustion chamber compared to the second which leads me to believe that they are CNC machining the combustion chamber. Plus the tool doesn't look like a tool that would normally be used for port/polish.
It's been a long time since I've done head machining though, so take what I say with a grain of salt.
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I agree.
I'm new to the BMW world... is getting ported/polished heads or service not typical?