Some More Cylinder Head Porting Background

The cylinder head is the most important part in an engine where substantial time and effort is spent by a professional tuner. There is more power to be gained in correctly porting the cylinder head than in any other modification that it can be done to an engine.

Cylinder head porting is the process of grinding material from the ports and chamber of the cylinder head to increase the airflow and thus improve performance of an engine.

The flow efficiency of the cylinder head will determine the horsepower potential that an engine can achieve and by correctly porting the cylinder head, higher level of efficiency is achieved and the engine will extract more power.

The cylinder head consists of three important areas which are the intake section, the combustion chamber section and the exhaust section. It is very important that all three sections are modified to work in conjunction with one another as power will suffer and engine efficiency will decrease considerably. I cannot stress this enough as every day I come across ruined heads after being ported badly and my point is that it is useless to have a huge high flowing polished inlet port and the combustion chamber is all shrouded and will not burn it efficiently or the exhaust port does not flow enough air or has a bad shape or the inlet/exhaust flow ratio is out as the engine will not produce more power or even worse decrease its power after being ported.

Another important topic is engine characteristics. Cylinder head porting needs to be accustomed to the usage that the engine will operate at. A head modified for drag racing operating between 7,000 and 10,000rpm will be useless to a rally engine needing more midrange torque and operating between 3500 and 7500rpm.

When a new client comes to our workshop with a cylinder head to have a porting job we ask several questions so that we can tailor the porting appropriately the type of driving the engine will operate in.

If the engine is going to be built in house then we know most of the answers but if a client come with just the cylinder head than we need to make sure to have all the required information so the cylinder head porting will be done accordingly.

Just to give you some idea these are some of the questions that we ask:

a)Is the engine for street use, off-road/rally, circle track or drag racing?
b)Is the engine normally aspirated, turbocharged, supercharged, NOS, or a combination?
c)Engine size, Bore, stroke, connecting rod length?
d)What type of fuel is going to be used? Pump fuel, racing leaded fuel, alcohol?
e)Is the engine carbureted or electronically fuel injected?
f)Will the car have a full exhaust system or open headers?
g)Is the camshaft still stock, and if not we need full specification.
h)What is the weight of the car and type of transmission and gearing is used? Manual, auto, sequential?
i.etc

After all the questions are answered then we can start the cylinder head analysis and port the cylinder head accordingly.

Next time we will post some information and pictures of a Mitsubishi Evo 4G63 turbo head we just did for street racing.

If you would like some help or require my service please contact me at cjpowertuning@yahoo.co.uk