Hi,

Does anyone know all the benefits and drawbacks of porting and polishing your head?

Fuel economy?
Heat?
Horsepower?
Torque?
Reliability?
Noise?

fuel economy: a mild port will actually improve fuel economy, and if youre going for a more extreme port job then i dont think youre too woried about fuel economy.
heat: i never heard of porting having any effect on how an engine runs, unless you end up runnin lean because of the higher air flow.
horsepower: sometimes nothin to get super excited over 5-10hp, but ive heard guys who have dynoed their cars and seen almost 30 hp increases
torque: ditto as hp
reliability: should have no effect on reliability
noise: well if youre runnign a cold air intake you might notice that the whooshing sound gets a little louder otherwise there shouldnt be much of a noise difference.

Thanks for the info. I am looking into doing that while in the process of changing out a head.

Your MPG will go down no matter how you look at it. More air in ='s more fuel used.
HP/TQ increse will depend on how wild the port job is.





95 Cobra
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"Your MPG will go down no matter how you look at it. More air in ='s more fuel used. "

gasket matching and smoothing out any imperfections in the head/intake castings will improve your gas milage.

on a 3.1 cavalier the air intake is read through the map sensor and info from the 02 sensor, you fuel use is determined by vacum and your air fuel/ ratio , if you have imperfections in your intake/ head the air you are taking in is not used as efficiently as it can be, although the o2 and map still read the same information, if you smooth out the flow the air taken in will flow smoother and provide better combustion with the fuel injected into the motor. even though you inject basically the same amount of fuel into your motor as you did before the motor will use the fuel more efficiently and you wont have to give the car as much gas to provide the same amount of acceleration, because of increased efficiency in the burning of the gas you actually save gas and your fuel economy gets better. now if were talking about opening the ports up and modifying the path of airflow as in a more radical port job, the air flow is faster and straighter. you will be taking in much more air therefore using more gasoline.

=D

2 things to add.

heat: if its a badly done port job and the exhaust ports are opened too much they can add heat to the collant, i have seen this done befiore.

MPG: a mild port job will help for the reasons stated above, by making everything flow better. Same thing with adding a perf exhaust system. The reason why most see MPG go down is because they are using the extra power offered by the performance parts. If you always floor it your gonna loose MPG, if you regualte your foot better, you'll see a gain in MPG. This only applies for mild performance enhancers. Anything to radical kills MPG no matter what.