We know that Valves IN are bigger than Valves OUT.
I spoke with a mechanic and he told me that if we change the Valves OUT and put the same size as the Valves IN probably we will take 1-2 hp.
If you want to do this check out Ferrea Valves on ebay. ~$2-300 for 1mm oversized valves. I think you can enlarge the Intake port by 1mm and the exhaust port by 1mm and you will see some benefit, but like JRODSVT said you will lose some torque by matching the sizes.
Ferrea Competition Plus Valves have built a reputation as the industry's most reliable extreme duty valve. We, at Ferrea, are dedicated to providing the absolute best product on the market.
Our extensive R & D programs provide tehcnological gains, which are implemented in each of our competiton plus valves. They are engineered for higt rpm, high horsepower racing engines, and are chose by many top NASCAR, Drag, and Oval & Sprint Car-racing teams.
To manufacture the valves we use special aerospace quality alloys, including EV8-Z18, which provides high tensile strength. An exclusive two-step slow forging process ensures proper grain flow and virtually eliminated any damage to the material structure. The valves are then heat treated and stress-relieved over a 48-hour period, which is the crucial base of our molecular integrity. These valves feature avionics-quality hard chrome along with a specially applied hard tip. Our engineering staff at Ferrea spends countless hours conducting flow bench tests to achieve an optimum balance of flow, velocity and efficiency in the design of this valve. As a result, these valves incorporate smoother radiuses and unique undercuts. These exclusive features are what make the Ferrea Competition Plus Valves unequaled in performance and reliability!
Ferrea is once again setting the pace with its Competition Plus PQ Series Exhaust Valves, the next generation of exhaust valve technology.
Due to the evolution in today's competition engine applications, temperatures are increasing and as a result, longevity is decreasing. Therefore, Ferrea is pleased to introduce our NEW! Competition Plus PQ Series Valve.
This is a next generation exhaust valve made of an Ultra High Strength, High Temp Nickel Stainless Stell Alloy. Ferrea first used this material with great success during the development of a very high stress, high temp endurance racing program.
This PQ Series next generation exhaust valve material will progressively replace Competition Plus Series valves as applications evolve and the material becomes necessary.
Listed below are some qualities of the Next Generation Exhaust Valve material:
* Tensile strength increased by 20% at high temperature
* Fatigue resistance increased by 20%
* Valve seat life increased by 25%
And trade off some low-end torque, even if you match them... Larger valves almost always equals weaker bottom-end torque. That's why trucks have small valves and ports- it promotes low-speed velocity and effeciency.