porting head etc

[timthetinyhorse 0]

this may sound like a silly question but im new to working with engine internals and i want to learn more, when reading about cams etc i understand the idea of increased lift and duration but what difference does a ported and polished head make and what exactly is ment by this?

Are there any real gains to be had by porting and polishing over just changing to KR cams in a 9a?

 

Thanks in advance and sorry if it a daft question

 

Rob

[davidwort 0]

yes, a well fettled 16v head will make the engine more efficient, powerful and give better torque throughout the rev range, a bad one may rob power and torque. Done well 10-15% or more power at peak.

There's a range of things that can be done,

simply smoothing out imperfections in the casting, matching the manifolds mating cross sections to the head faces and modifying the area around and behind the valve seats and throat.

The combustion chamber in the head can be smoothed and polished to help reduce pinking under higher ignition advances or with increased compression that enables more power.

A skilled engine builder with a flow bench to measure improvements in flow through the ports as modifications are done, will also match the combustion chamber sizes precicely to balance the engine and further release power, ultimately 'blue-printing' and precicely matching the volumes, weights and dimensions across all cylinders.

Unfortunately quite a few so called 'ported and polished' heads are nothing more than an exercise in bling and size boasting, the result is often inlet ports opened up far too wide, reducing the velocity of air entering the head and messing up low and mid range torque.

[timthetinyhorse 0]

also how does skiming the head i.e. increasing compression improve performance on N/A cars?

[timthetinyhorse 0]

thanks mate, very good definition, have been looking at a few websites and people are saying around £550 for a head port on a 4pot engine, will a new exhaust manifold etc also help with the gains involved alongside cams

[davidwort 0]

you can't really skim a 16v head due to the design, a small amount can be taken off if a head gasket has gone and the head slightly distorted, but it can only really be done once

in general skimming to raise compression will allow you to develop more power from the same capacity engine, provided the right engine management is used, i.e. suitable ignition and fuelling controls, but again, the 16v is pretty high compression anyway and short of running on race fuel you really do risk pinking and engine damage.

A 4 branch manifold may gain a little peak hp, but the standard 16v cast iron manifold flows well and it's probably a more reliable alternative to internally polish and port it instead.

[timthetinyhorse 0]

ok thanks mate, plenty for me to think about there,

im on the hunt for power but i realy like the way a N/A engine provides it power over turbos.

[Abdul 0]

ok thanks mate, plenty for me to think about there,

im on the hunt for power but i realy like the way a N/A engine provides it power over turbos.

 

 

Same here, N/A really lacks the bang for buck factor though unfortunately lol.