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Cylinder Head

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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 (also called engine head) available. This is the one area that will potentially give you the greatest increase in engine power. Why? Well, as Langer explains 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.

Cylinder Head Porting

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.

Cylinder Heads side view

If you're intent on trying cylinder head porting, the first thing that you need to know is that porting heads 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 die-grinder, but electric die-grinders don't operate at a high-speed like pneumatic die-grinders. You could also use an electic 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.

How To Port Cylinder Heads

Crached cylinder head

If you've read all that, bought your air compressor and your die-grinder, and gotten hold of a few spare engine 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.

1. Right, we'll begin by looking at the camshaft before moving on to the car accessories you'll require to port your cylinder head, the basics of gas flowing and cylinder head porting itself. Before we can get started, we need to strip down the engine head; remove the camshafts and camshaft pedestals, then remove the valves, valve springs and valve stem seals.

2. You should also remove all manifold studs. With everything stripped, you need to inspect the cylinder head for cracks. It's no good porting a cracked cylinder head, though a cracked cylinder head may still be good for experimenting on, so don't throw it away! The most likely areas where cracks will appear are between adjacent valve seats, and around the valve seats, especially around the exhaust valve seats. You may need to some emery cloth to remove any carbon deposits to do a thorough check.

3. If you don't see any cracks, have the cylinder head thoroughly cleaned in a chemical bath. You can dip a cast iron cylinder head in a hot caustic solution but don't dip an aluminum cylinder head in it! Caustic solution will react with the aluminum and give off an explosive gas! For an aluminum cylinder head you should use Trichloroethane. If you don't have access to a chemical bath, you can use engine cleaner and a stiff brush to get oil and gasket pieces off. Once the cylinder head is clean and dry, use a sand blaster or a wire brush to clean off any stubborn carbon deposits.

Ported cylinder heads
Cylinder head porting

4. Once that's done, do another thorough check for cracks. If you don't see any cracks, have the valve seats replaced and the valve guides removed by a reputable engineering shop. Replacing the valve seats are not crucial as long as they're in a good condition. However, you must have the valve guides removed.

5. We'll get to enlarging the port in a while when we discuss gas flowing; but for now we'll focus on the main aim of cylinder head porting, which is to smooth and straighten out the ports. If this is your first attempt at cylinder head porting, I'd suggest you try to master that first.

Main aim of cylinder head porting

6. Starting air intake ports, use a flame-shaped carbide and attempt to remove any obvious bumps and crevices in the port without removing too much metal, then try to straighten the post so that it has a consistent size from the mouth to the point where it curves into the valve throat. Remember to move the carbide all the time and don't hold it on one spot as it will quickly create a hollow that will be difficult to remove!

7. Once you're happy that you've got your first port nice and straight you can use a grinding stone to smooth it if it's a cast iron cylinder head, or a sander band if it's an aluminum cylinder head. Now try to replicate your work on the other ports. Use an inside caliper to make sure all the ports are the same size.

Remove any obvious bumps of cylinder head porting

8. Now, working from the valve throat side, use an oval carbide to blend the short side radius. Again, try not to remove too much metal. Also remember that you want a smooth flow through the valve throat area and that you want a consistent port size through the length of the port.

9. Once you have blended the short side radius, turn you attention to the long side radius where the valve guide boss is located. Use an oval carbide to flatten the valve guide boss until you have a consistent port size from the manifold face to the valve seat.

Remove any obvious bumps from the valve throat side