Edelbrock Cylinder Head Flow Data

When comparing airflow numbers between heads, there are several things to consider. These are general guidelines... not absolutes... but guidelines that should be considered when purchasing cylinder heads.

1. YOU MAY NOT BE GETTING "APPLES-TO-APPLES" COMPARISON
Flow bench measurements are only useful and accurate when done carefully and on a calibrated bench. Proper alignment of the head with the bore is required to simulate exact geometry of the engine. Accurate lift measurements are also required. Finally, atmospheric conditions are needed to interpret the data. As a result, you may not be getting an "apples-to-apples" comparison when comparing numbers from different benches.

2. 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.

3. 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.

4. 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 power.

5. 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.

6. WHAT'S THE PRESSURE DIFFERENTIAL?
The pressure differential that a head is flowed at dramatically affects the results. All Edelbrock cylinder heads are flowed at 28" of water, which more closely represents what an engine will see. Beware of companies flowing heads at anything less than 28" of water, because that is not a valid comparison with Edelbrock heads.