Chevy High Performance BB Chevy
Flow Figure "Spreadsheet"

NOTE: All flow figures were obtained using a 4.250" bore fixture and exhaust figures were compiled using an Amduri 2.25" test pipe. All information was recorded using the same Superflow 600 flowbench and fixtures. (All of this info can be downloaded off of the Chevy High Performance magazine website @ www.chevyhiperformance.com . )

Cylinder Heads used for testing are as follows:

Intake

NOTE:

AFR 315cc exhaust flow figures were obtained using the optional tulip valve that comes standard on the AFR 335 and 357 cc packages. The standard valve that comes with the 315cc package would flow approximately 10 CFM less (Refer to our website or latest catalogue for exact flow figures.) AFR feels 84% is actually too high an intake/exhaust ratio for a normally aspirated engine and utilized the different exhaust valve to bring the ratio down to 81%.

IMPORTANT:

Many of the competitor's cyilnder heads advertised in this testing have MUCH LARGER intake runner volumes. Keep that in mind when evaluating the flow figures advertised. AFR also offers larger intake runner volumes that will be tested shortly. (Refer to our website or our latest catalogue for accurate flow figures on the entire Big Block product line we offer.)

VERY IMPORTANT:

All flow figures taken in this test were recorded using a 4.250 bore fixture. Current chamber designs and valve sizes used today (typically 2.250 - 2.350 for BBC intake valves) would show better results being tested on the larger 4.500 bore fixture. (Primarily due to unshrouding the valve with the larger bore size.) With so many production GM blocks, as well as the aftermarket, starting at 4.500 inches in bore size, we feel this is much more representative of the current trend in Big Block Chevy engine building. All published flow figures from AFR were obtained using a 4.500 bore fixture. However, the fact that all the information obtained at Westech was recorded using the same bore size (4.250), the same flowbench, the same operator, etc., this still proves to be a valid test and comparison, eliminating many variables that could potentially exist evaluating and comparing flow data.

The following information was recorded the same day at Westech, flowing the exact same AFR 315cc intake port, simply swapping test fixtures to the larger 4.500. These flow figures are almost identical to the published figures from AFR. They are as follows: