Im not expert in moding engines, but like you guys I have looked on the internet for info and how to's over the past 5 years.. You're not going to find any reputable how to's, the most information I been able to find was by reading certain treads on this and one other forum. Anything that comes from Motorman and EdwardN (formerly TopGun777) is reputable on this forum. On the RCZone the one reputable guy I found goes by the name of Maverick.

That said, you will ahve to read tru a lot of post to learn anything, the most I have found are bits and peices of info where they descrive what some of the modifictions do, but there's a lot more detail that most people dont know about, stuff that you learn by trial and error.

As far as ploshing the engine. What I have read is that you can polish the inside of the crankshaft, and if you're going to put a fuel scoop on the web of the crankshaft, the scoop wont work unless the intake channel and the scoppare polish vey fine. THeone thing you shouldnt polish is the sleeve. The roughness of the sleeve and the cuts on the sleeve help atomize the fuel. Whats meant by atomizing is, the fuel mixture goes from a liquid to a fine mist. The fine mist makes it easier fot the plug to ignite the mixture.

Again, Im no expert.