As we try and figure out how make our cars go faster, we often find ourselves going through hot rod or tuner magazines, and read what the featured cars did to attain those extra ponies. Changing camshafts is one way to get them. But we often see the term head works. A camshaft basically dictates how long an intake valve or exhaust valve stay open. Changing the size of the valves can also determine the amount of air/fuel mixture entering the chamber. These are what we call head works. Meaning, altering or modifying cylinder head specifications from factory or stock specs. The cylinder head plays a key role in how an engine breathes better.
One way of making the engine breathe better is to match port or polish the intake and exhaust ports, and match it (internal diameter) to their respective manifolds. This minimizes any minor obstructions that may hamper the flow of air/fuel mixture to the chamber and as the burned mixture leaves. If you mount a stock head on a flow bench and compare it with a modified head, and you get a 3-percent increase in flow rate, that is good. Efficiency is still the goal when you massage any engine. You can go one step further by changing the shape or size of the ports. By doing so, you can increase the flow rate but it would have to match the specs of your cam. If not, it can affect the drivability of your car. By having the wrong port designs, your engine will drown from the excess flow of air/fuel mixture or it can starve. It is possible for the air/fuel mixture to swirl or stay to long in the ports before going into the chamber even when the intake valve is open.
Shaving the head is also a way of increasing power. When you shave or machine the part of the cylinder head where the combustion chambers are located, you decrease the volume of each chamber. By doing so, you increase the compression ratio. Increase the compression ratio and you get a stronger bang. Again, too much you can cause problems. This is also done if the cylinder head is warped. A problem there is they shave the head to make the cylinder head square again. They don’t compute for the new compression ratio. The increase in compression ratio is an increase in power but also an increase in head temp that can cause overheating problems.
Part of changing your camshaft is upgrading your valve springs. Hi rev springs as some would call them. Stiffer valve springs means your valves will close faster as revolutions per minute increases. It also minimizes valve float. Valve float is when the camshaft moves the rocker arm, moves the intake valve or exhaust valve with enough force that the valve is left in the open position longer that it’s supposed to. Why is it not good you ask… because if the valve doesn’t close on time, the piston might hit it on its way up. A trick that some do is they look for valve springs from a diesel engine that can fit their existing cylinder heads. Most of them have dual springs. Something you might notice after installing stiffer valve springs is when you start up your engine, the starter may have a harder time turning the engine over. That’s because the starter has a harder time moving the valve train. A slight draw back but once it starts….
A decent shop will often ask you what kind of performance you are looking for and how much you are willing to pay for it. Performance doesn’t come cheap. Reliability should always be considered. Although a piston with a hole on top makes it lighter, it doesn’t make your engine more reliable.