When it comes to getting the most power out of a naturally aspirated engine, the key area that you must focus your attention on is the cylinder head. This is the one area that will potentially give you the greatest increase in engine power. Why? Well, as we explained in engine building and power basics, the key to increasing an engines horse power is to get the engine to ingest more air and be able to expel the resultant increase in exhaust gasses, in other words, getting the engine to pump more air by increasing the air-flow in and out of the engine. But we must achieve this while ensuring that the gas velocity remains high enough so that the fuel in the intake charge does not drop out of suspension as this will hinder efficient burning of the fuel, reducing power and increasing consumption.
On a motor car engine, there are three areas that can affect air-flow and where you can make improvements. These are:
- The intake system, which includes the air filter, plenum and the intake runners.
- The exhaust system, which includes the exhaust header, catalyst converter and the mufflers.
- The cylinder head, which includes the cylinder head ports, valve area and the camshafts.
We've discussed the intake system and the exhaust system elsewhere on this web site so now it's time for us to turn our attention to modifying the cylinder head. However, in this section we're going to discuss a little bit more than just the cylinder head, we're going to discuss cylinder head porting, gas flowing and power tuning the cylinder head, old school style! We'll also be discussing performance camshafts, cam timing, valve timing and valve overlap.
A word of warning though, cylinder head porting and gas flowing is a rather advanced form of car modification and is not for the novice or for the faint of heart. Cylinder head porting is a skill that must be developed and honed by hours and hours of practice. If you're intent on trying cylinder head porting, the first thing that you need to know is the porting always begins by trial and error so if you're going to do your own cylinder head porting, start on a cylinder head that you can afford to total, in fact, start with a couple that you don't mind loosing. Otherwise you should leave cylinder head porting up to a professional with a flow bench. The other thing to note is that cylinder head porting requires some rather expensive tools. You'll need a high-speed extended pneumatic die-grinder with carbide and steel grinders, and a high-pressure air compressor (no, we're not talking about turbochargers here) to power the grinder. You could use an electric die-grinder rather than a pneumatic die-grinder, but electric die-grinders do not operate at the high-speeds that pneumatic die-grinders do. You could also use an electric drill rather than a die-grinder but you won't get the same results as you would with a longer, more agile and thinner die-grinder. An electric drill also does not operate at the high-speeds that a pneumatic die-grinder does.
A dremel tool, which is much smaller than a die-grinder can also be used to port smaller objects like the oil channels in an oil pump, and can be used to deburr sharp edges in the combustion chamber and on the top of the piston.
Right, if you've read all that, bought your air compressor and your die-grinder, and gotten hold of a few spare cylinder heads, despite our warnings, then we can move on and start modifying the cylinder head for extreme power. But remember that we did warn you. Right, we'll begin by looking at the camshaft before moving on to the equipment you'll require to port your cylinder head, the basics of gas flowing and cylinder head porting itself.