Originally Posted by Bluethumb
And what's the benefit of maching the ombustion chamber? Is it only to make sure there is clearance?
You get rid of the sharp edge on the combustion chamber which can be a hot spot and cause pinging on higher performance engines. Better flame spread, more of a squish band, etc. For your purposes, I think you'll be perfectly happy not going to the extra trouble. If you wanted to hot it up a bit more though with higher compression pistons you'd need to do that to avoid interference.