Porting and gas flowing engines.

Porting an engine
The inlet and outlet ports on the engine block are usually larger than those of the manifolds that connect to them to help cope with mismatched alignment. Most are far from smooth due to the casting process so small gains are there to be had by smoothing out and polishing the insides. Engines need to breath as freely as possible and obstructions cause turbulence and this is not very good for airflow. The air intake port would not benefit by opening up to match the intake manifold so most port matching work is best performed on the exhaust ports. A word of caution though if you enlarge the exhaust port fully to the size of the gasket when the manifold port opening is smaller than the gasket you will completely mess up the airflow and will lose power - the aim here should be to get the two port openings to roughly the same size. Really as far as a DIY approach goes do little more with the ports and manifolds than a smoothing up and polishing.

The most important area within the engine, as far as air flow is concerned, is the valve seats and bigger power gains can be has here especially for engines with slightly higher lift valves with some careful blending below the valve seat insert to remove the steps and grooves.

The angles on the seats is also of concern to the engine tuner. Generally the thinner the seat the more unreliable the engine will be so we are back to the eternal compromise. Because each engine type is different with some producing more heat than others and 20v 16v and 8v systems you are better off leaving head work to the professionals who are able to measure the airflow through the head and help create the perfect head setup for you. Each type of engine is better suited to a specific valve seat shape. Fitting larger valves will generally improve the airflow through the head of the engine into the combustion chambers and will help the engine cope with a much higher state of tune. Adding longer valve stems will also release a little more power too.

Caution – if the airflow is too free then the engine will lose it’s torque and can be totally un-drivable below 2000 revs.

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