Quote:
Originally Posted by blykins
I would imagine the port volumes are huge. With 400cfm, they would have to be. This probably wouldn't be the kind of head that you would want to run on the street. It would require a large cam duration to use the airflow.
Large ports, slow port velocity, and large camshaft durations equal less than desireable street manners....the equivilent of trying to drive a Nextel Cup car around town to get groceries.
I would consider using these, but it would be a very large displacement small block 445-460ci.
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Quote from the head designer/builder Chuck Hebestreit
" It needs to be explained that these port are a maximum effort type head. While they are to some a large port, they are small compared to others. The velocity can be somewhat controlled by camshaft profile. Having owned Howards cams for years in the past, I understand head/port/cam/manifold interactions fairly well. All that being said, the velocity it better in this head than that of the 351 Cleveland and Boss 302. Without going into theory and fluid dynamics, the entry cross section of the port is smaller than the previous mentioned heads. At some point there will no doubt be several people holding and testing these heads to confirm everything I claim. When the exact figures are know, I will get them out and the measuring can begin. The 400 cfm is at .800 valve lift which is also not a street friendly number. In respect to numbers, the cam manufactures agreed to use .050 lifter rise as a published value for their cams so that people could compare mfg. to mfg. It seems for most "true" high performance heads, .800 lift is a fair figure to compare. While NHRA Pro Stock engines use even greater valve lift, there is not much need for a valve lift of .800. The hemispherical chamber allows for great low lift flow and less turbulence. Turbulence can affect flow velocity in a very negative way.
I have driven my ProMod on the street here in Flagstaff and once ran the Top Fuel Dragster on the streets of Long Beach California, but I don't consider those as street driven cars.
I will make smaller port versions available if needed, but those heads would be simply jewelry.
Of course a larger displacement would be beneficial. The test engine is 347 cubic inches. 4.125 bore x 3.25 stroke. All the real world data that I give will be from this engine. I am using a new generation Boss 302 block. I can't speak to all of the blocks made so far but I will say the one I have is absolutely beautiful. I am partial to the Boss 302 because I set my first Land Speed records many years ago with a Boss 302 in a Pantera at El Mirage dry lake. We set a record every time we unloaded that car for 2 years running. I believe one of those records still stands 20 years later! If someone breaks it I will dust off the Pantera and go get it back!"