At what point does a difference in flow numbers actually make a real performance difference? Does a head that flows 280/230 perform much better than one that flows 300/250? (assuming we're comparing apples to apples with flow measurements). With HP, there isn't much diff. at all between 420 and 430 hp, for instance.(few people would spend a grand to pick up 5 hp...)
petegtsv10
You can't draw any meaningful conclusions from just looking at head flow numbers. Just because one set of numbers is larger than another is no guarantee of anything. You have to look at valve size, intake vs exhaust flow , cam timing, engine size, operating range, etc. You need to use some engine modeling software like Dyno Sim to properly evaluate different heads.
Frank
Frank
From the Edelbrock website:
Bigger is not always better!
A large port doesn’t always mean more power. This is especially true with street heads and in some cases, race heads. Velocity is just as important as flow. A smaller port volume generally equates to higher velocity for better street performance. The speed of the mixture determines how tightly the combustion chamber is packed. The more tightly packed the combustion chamber, the more pressure is developed when the mixture is ignited, pushing the piston with more force for more power. For example: A large port and a big flow number at 0.600" lift means low velocity (especially off-idle to 3500 rpm) and results in less throttle response. For the street, velocity is the key to overall performance.
A large port doesn’t always mean more power. This is especially true with street heads and in some cases, race heads. Velocity is just as important as flow. A smaller port volume generally equates to higher velocity for better street performance. The speed of the mixture determines how tightly the combustion chamber is packed. The more tightly packed the combustion chamber, the more pressure is developed when the mixture is ignited, pushing the piston with more force for more power. For example: A large port and a big flow number at 0.600" lift means low velocity (especially off-idle to 3500 rpm) and results in less throttle response. For the street, velocity is the key to overall performance.
Compare peak flow and low lift flow.
Cylinder head buyers have a tendency to only consider peak flow numbers. It’s important to look at all the flow numbers, from .100" to peak, in order to determine the performance level of a head.
Cylinder head buyers have a tendency to only consider peak flow numbers. It’s important to look at all the flow numbers, from .100" to peak, in order to determine the performance level of a head.
Type of valve influences flow.
The type of valves used will influence how well a port flows. A valve with an undercut stem is less of a restriction to flow and will allow a port to flow more, filling the cylinder better and producing more ower.
The type of valves used will influence how well a port flows. A valve with an undercut stem is less of a restriction to flow and will allow a port to flow more, filling the cylinder better and producing more ower.
Consider this fact for street applications.
Generally, in a street application, the smaller the valve diameter, the better the velocity and flow will be with the correctly sized port. This holds true for both the intake and the exhaust ports. When you can equal the flow of a larger port and larger valve with a smaller port and smaller valve, you have a much more efficient port, which will generally make more power and use less fuel.
Generally, in a street application, the smaller the valve diameter, the better the velocity and flow will be with the correctly sized port. This holds true for both the intake and the exhaust ports. When you can equal the flow of a larger port and larger valve with a smaller port and smaller valve, you have a much more efficient port, which will generally make more power and use less fuel.
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