SBM Edelbrock/Speedmaster Head Data

pittsburghracer said

I understand that and trust me I’ll be reading along but a 170 cc chamber will only flow so much so why not port the head then try to find the extra 10-15 cfm I guess you are hoping to find. Look closely at the chamber around both the Speedmaster and Edelbrock head and you will see why the speedmaster flows more. Valve shrouding. A man way smarter than I will ever be preached 15 max on the valve angles and hopefully under that number. That number seems to really come into play up top. Ex: 90-70-60-45-30-15

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One more comment/observation about the top cut angles. Again, recognizing that I could be wet behind the ears, in a perfect chamber the top cut off of a 45 degree seat should be in the 35-39 degree range. This applies to valve angles of less than 14 degrees (mopar is 18 so some concave cutting must occur on the spark plug side to reduce shrouding). This allows for the slow expansion and pressure recovery once the air is past the valve. Even a 15 degree (so a 30 degree top cut) turn after the 45 degree seat is too much and turbulence will occur and shut down part of the flow area.

This information is from two of the top cylinder head developers in the country. But, I recognize my interpretation and application could be wrong.