Q4 Head Modification

Over the past eight years we have been developing ways to enhance air flow and port velocity on 4-valve cylinder heads. From designing and developing our own valve seats and guides with specialized seat profiles, we have become one of the country's premier cylinder head performance centers. We are now proud to be introducing the Q4 cylinder head program.

Q4 Performance Head

The first thing that needs to be understood about modern-day 4-valve heads is valve lift. In most applications these heads have a lift of .375" - .450". The important thing we must do with all heads is improve both their air flow and port velocity. Remember, all air that flows through a head must pass over a valve seat.

On a Q4 head we use four completely different valve diameters. We will examine the port tunnels and flow test a stock head to learn which port is weaker on air flow as we will flow each port quadrant separately. After seeing which port quadrant has the lesser flow of the two - either intake or exhaust - we will install a different size valve. Along with installing a different valve we will also change the valve contact angle. We have found that certain degree contact angles flow better at low lifts than the standard 45 degree seat. Further, other degree angles flow better at high lifts. So we have valves manufactured to match our specified contact angles for each Q4 cylinder head application. All Q4 heads include new Pro-1 Racing valve seats and guides. All of the valve seat profiles are CNC machined on our state-of-the-art NEWEN head machine, which has been the standard in all high performance cylinder head design shops. We can design the valve seat to your specific cylinder head application, which can consist of many different valve seat profiles and radius'. We will then port each quadrant to meet the standard or oversized valve. With this you get the best of both worlds regarding air flow. One valve quadrant is getting optimum air flow at low lifts and the other quadrant is getting optimum flow at high lifts.

Another issue with 4-valve heads is their combustion chamber air flow. In most heads the air flow is measured as "air tumble." What this means is when the intake valves open the incoming air tumbles over the piston in every which way as it is rising on the compression stroke. You can be assured that the engineers who design cylinder heads put a lot of design time into air tumble. Besides getting air tumble, with the Q4 head design, we also introduce "air swirl" into the combustion chamber. Air swirl happens as the incoming air makes a circular motion inside the cylinder. We find air swirl in all 2-valve cylinder head applications. Think about having the benefits of having both air tumble and air swirl in a combustion chamber and how it will enhance the fuel charge burn.

You may ask, "If this design works so well, why don't the OEM heads have a Q4 design?" The answer is simple: the manufacturing costs to mass-produce such a complex head design for their standard heads would be too high. The higher the cost, the less interest the manufacturers have in it. But here at Pro-1 Racing Heads, we can make these heads a reality to consumers who desire enhanced engine performance. And you can rest assured knowing we are the first to introduce this service to the motorcycle industry.