New header from singapore

this is probably out of topic but does kinda have to do with subject...how does a port and polish help us??what do they go for in the states??

 

Pulled from Skunk2. An average pnp job ranges in the $500+ area

When a specialist ports a head, he or she is looking to maximize the volume of air entering and leaving the head without losing velocity. Volume is important because when you draw more air into the cylinder, the engine demands more fuel, which results in more powerful combustion and subsequent gas expansion. Maintaining velocity ensures the increased volume reaches the cylinder. Many specialists have their own method of achieving this goal, so no one way is necessarily the absolute right way. The current school of thought generally employs a flow bench and pitot tube to measure air flow and air velocity, respectively. With these tools, the ports can be tuned for a given application. Forced induction or all-motor, street or strip, the head can be optimized to suit your needs.

The goal of porting is to reshape and refine the ports. Factory heads usually have surface imperfections from the machining process and sand casting that are not cost effective for the factory to remove prior to mass production. Therefore, flow taxing turbulence is present in most heads. To counter this problem, the head porter's goal is to straighten, streamline and polish the pathway of the port, uncorking the airflow traffic jam. Air moves the fastest on the bottom of the port (or the port floor), which is the shortest route to the valve. Thus, optimizing the floor is particularly important. Maintaining adequate velocity is essential for performance, since the volume of air is ineffective without getting it into the cylinder as quickly as possible. Some recommend shaping the floor, while others feel the factory shape is adequate and only needs to be enhanced and polished. Either way, refining the port is beneficial.

Some high-performance applications take porting one step further and refine the "bowl," the curved section before the throat. This is usually where the valve guide protrudes into the port. To reduce the impedance caused by the valve guide, some porters will grind away the portion that protrudes into the bowl. This technique, while effective, is not necessarily recommended for a street application, since the valve guide's durability and reliability are reduced. Also, depending on the valve angles and the general design of the combustion chamber, the ports may also be shaped so the bowl guides air into the cylinder with a minimum amount of intake charge lost out the exhaust port during overlap.

 

great find there serious!! really helpful... ill most likely be looking more into this in the future at some local shops

 

thaty looks pretty good...

 

Too bad they dont make it for the PZEV :cry:

 

...or 2.4L

 

any sound clips?