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Head work is a common topic around a performance motorcycle. Although many people either neglect or simply do not understand the theory's and facts behind working over a set of heads. In this article we will discuss the merit and the pros and cons of working over a set of heads. When a set of heads are going to be ported and polished the entire package must be brought into the formula. Don't just "hog out" all the ports and expect better performance! The ports and valves must be matched to the camshaft, carb, and exhaust to optimize performance for the way you ride. If the heads are over ported, it is like placing a carburetor for a big block on a Yugo. Sure it will work, but you are not doing what the engine needs to achieve peek performance for that combination. Porting When a set of heads are being ported you want the diameter of the port to coincide with the flow rate of the air as well as the RPM the engine build peek power. If you want maximum power at 3500 RPM do not expect the bike to breath well at 7000. If you want it up high, don't expect it down low and so on. If the heads are ported to a mirror shine in the intake runner that is not always the best idea. It is great for high RPM usage but will do more harm than good around town. When the intake ports are very smooth the air is not tumbling well and the fuel has a tendency to puddle in the port by falling out of the air on the way to the combustion chamber. A little tumble is always good for a street bike as it will help keep the mixture that the carburetor has put together. Mirror polishing the exhaust is always the way to go. Get that stuff out as fast as you can! That will help the engine a great deal. The most important section to look at when porting heads is the inside radius of the intake and exhaust port behind the valve head. This is where many "eddies" are created and can actually suck the air back out of the combustion chamber. It works just like the whirlpools you see in a river, avoid them at all cost to get down stream. Polishing the combustion chamber will not do any good accept for around the exhaust valve where it will help the exhaust to round the corner on its way out. Most people do this to prevent carbon buildup in the combustion chamber. This is fine if you are running a high compression engine, you don't want any buildup. The most important point is to port the heads to the
way you ride and the engine combination that you have chosen. If you
have any questions about this feel free to e-mail us and we can answer
any of your questions. Ziyad Showket
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