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PORT FLOW AND VALVE CHOICE

PORT FLOW AND VALVE CHOICE


What does the valve have to do with the flow of the port?
The profile on a valve has a huge effect on the flow stability in a port.
Over the last few years I have spent an enormous amount of time on the flow bench developing ports for not just for my own Cleveland heads, but for other independent companies, and I find it incredible how much the valve profile changes the outcome, especially in the area of air stability as it races through the port into the chamber, and this is why.
Just as it is important to get all the physics right in a port design to suit the engine and conditions it will be used for, so is the valve. Valves play a key role in helping to maintain that important air flow stability all the way through the lift cycle.
The tulip profiles, margins, undercuts, back cuts can all help or hinder the quality of air flow that the port can deliver.
When a port is taken to a much higher level, (canted valved heads especially) the more sensitive they become to the slightest change in the conditions you are asking it to perform under, especially in the valve seat and valve design being used, they work together, split them apart, and they may not always perform as expected.
AFD use their own custom made valves the fits directly into AFD alloy heads and include the following spec:
• 21-4n stainless
• 1 piece
• Standard length intake 5.250"/exhaust 5.050" long
• Single lock groove
• Chromed stems and micro polished
• Hardened tips
• Under cut stems
• Swirl polished head
• Exhaust valves have a 22.5 degree tulip to stabilize exhaust flow averages across the lift range
• These valves are high quality items at a fraction of the big brand cost
• Price is for a full set of 16 valves
• custom manufactured in South America
AFD use their own valves for testing and flow results are based on the use of AFD valves.