The bowl area just under the valve head is where much of the magic will be created. A smooth transition from the chamber to the manifold is required to reduce as much restriction as possible. Increasing Flow Potential does not necessarily decrease low speed performance and throttle response. Only when making things larger for no other reason, can that detriment result. Shaping, contouring and blending allows high flow rates with smaller, higer velocity ports, thereby imporving throttle response, low end torque as well as upper RPM power. The valve guide, seat and bowl is completely re-shaped.

Just because Alloy heads are made from a softer material, doesn't necessarily make them easier to port. To the contrary, they could be considered more of a difficult challenge to get major gains in the finished product, since mistakes can more easily be made. The first thing we do is contour the port shape to specific dimensions for maximum flow, derived from our prior flow bench testing. Every aspect is addressed, and every detail is considered for the absolute maximum performance.

Undisputedly, most gains can come from serious modifications of the exhaust side of a cylinder head. Considering the air going in comes out of the combustion chamber expanded many times it's original volume, The exhaust port needs to be as good as it possibly can be. After first shaping the port to it's maximum flow, in this particular case, the factory divit cast in the port roof (bottom) is welded up using a TIG process, and then meticulosuly ground down, shaped, smoothed and contoured for optimum flow and minimal resistance. Note all the detailed aspects of the finished port, including the valve guide boss contour, as well as minimal and gradual changes which transfers air from the combustion chamber out into the exhaust manifold.

Like the Intake Port Bowl, the Exhaust Port Bowl also is an area of ultimate priority, where extreme attention needs to be applied to the hydro and aerodynamics affecting this critical area. Even the untrained eye can  visually comprehend the dramatic increases gained from this particular application and procedure. Even so, visuals do not tell everything, and can even be very misleading. However, the flow bench proved the worth of this modification by revealing a rock solid additional 7% gain over an already very impressive out of the box performance aluminum cylinder head. Those kinds of valuable performance gains are nearly impossible to achieve once all the peripheral components have been installed, and no further alternative options remain.

Not every cylinder head requires welding to improve flow, however, if maximum performance is sought after, then no punches are pulled! This type of dedication, attention to detail and quest for excellence sets Performance Unlimited's Pro-Porting© procedure apart from the rest. First, clay models and plaster forms are created and tested on a flow bench to arrive at the most advantageous port shape and design. Then that research data is transferred to an actual cylinder head by grinding, sanding, contouring and polishing. The end result is performance that no one else could ever attain, without  going to these same lengths… which is why there are winnders... and losers.

One of the most important features addressed is the very restrictive potential of Valve Shrouding in the combustion chamber. Here you can see the end result after material has been specifically removed (yellow) to provide maximum peripheral flow around the wall side of the combustion chamber, while retaining maximum gasket sealing surface, as well as  minimal chamber volume loss, which would in turn reduce compression.

Finally, the most significant aspect of this particular job is the combustion chamber. Serious chamber work involves a lot more than just taking off all the high spots and smoothening the surface. Meticulous care and careful shaping evolves a previously normal chamber into something able to withstand much more compression on lower octane fuel, with cooler running temps and much more air flow, thus increased horsepower. Note the MIRROR polish!

This particular Cylinder head is ready to go out to the Customer and ready to run. Each individual spring pressure and valve height has been measured and set to exact specifications. Nothing is left for granted.

Here is an example of what can be gained Using an Edelbrock 6025 Head. This chart proves it was definitely advantageous, gaining nearly
8% over an almost already perfectly designed after market aluminum head. If one could assimilate this percentage into directly into horsepower, that would mean an additional 35 hp for a 500 hp engine. Pretty significant stuff. Not only did we see notable gains from our modifications, the 'overall' improvement was considerable, compared to the stock OEM head, at an impressive 52% increase!