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Porting and Polishing should be done to your Honda to make the engine run smoother and breathe better. It involves replacing pieces to make more air flow through the engine. Thus, more readily available air to burn. Polishing makes engine run a bit smoother.



Porting & polishing are two steps or levels of the same process. The intake & exhaust runners (ports) in the head and manifolds are modified to increase flow. More flow= more power, but it's not quite as simple as that. It never is, is it? Both procedures require removal & disassembly of the cylinder head and the intake manifold. Exhaust manifolds or headers are removed as well. Polishing means exactly that- the runners are smoothed of casting flash and surface irregularities. Also the combustion chambers are smoothed and polished. The result is smoother, denser flow of gases into and out of the combustion chamber. A side benefit of polishing- small lumps & bumps in the chamber attract carbon deposits, which can superheat under load, causing detonation. Polishing removes these lumps & bumps, so your engine will be less likely to detonate. Polished chambers can allow you to run more timing advance, or more boost, or drive on cheaper gas than before the polishing job. EVERY engine taken apart to increase performance, should get a polish job. It's just good sense.

"Gasket-matching" is the next level of modification. The ports are matched to each other, using a gasket as a template. This is done to the head(s), intake, and exhaust manifold (or header) all at once. All runner transitions are made clean & smooth, from the intake, into the head, and out into the exhaust. Just like polishing, you should have EVERY engine gasket-matched if you are going so far as to take it apart to make more power. It's cheap, it works, and it's permanent (unless you wreck a head or change manifolds). If you have a die grinder, or a Dremel tool & some patience, you can do your own polishing & gasket-matching. Please do not try to do your own porting job. I don't want to hear about it.

Actual 'porting' is more elaborate, more artful, and more expensive. It is the modification of the size & shape of the intake & exhaust ports. Usually, the shop will ask you how much you want done. "A lot!" is probably NOT the right answer. The ports affect engine function like the camshafts do- they are made to function well at a specified range of RPM. Big hogged-out ports make more power at high RPM but will cause fuel puddling, stumbling, and even stalling at lower RPM. Once a port is enlarged, it cannot be 'de-ported" or made small again. For most street-driven cars (even the guys who THINK they will be running at 9000 RPM all day every day) a mild port job is all you need. The ports will be streamlined & opened up a little, giving more midrange & top end power, while keeping the ports small enough to maintain some off-idle torque.

Be wary of shortening valve guides for more flow, as this will reduce the life of the valves and the seats in the head. Be sure you can afford the long-term expense. There is a relatively new process called 'flow-porting', where the ports are enlarged by forcing a viscous, abrasive paste through the runners. This seems to work nicely, but my only experience with flow-porting leads me to recommend replacing all the valve guides AFTER the porting is done. The process can apparently open up the valve guides as well as the ports! The result was a fast Acura that smoked like a diesel.