The Brodix 195cc heads use a 2.02-inch intake valve and the 210cc features a 2.08-inch valve; both heads rely on a 1.60-inch exhaust valve. Burcham chose the Brodix LH 210cc heads, which come fully CNC-ported by noted engine-builder Keith Craft. Brodix lists the heads as KC-LH-F 210cc, noting the style of head and its CNC port job. He selected the heads for the large intake runners and significant flow numbers over the un-ported, baseline 170cc heads that had just come off the test engine.
A cylinder head's airflow is also critical when selecting heads for your engine, and there is a relationship to the intake port volume. Burcham explained, "The intake and exhaust port sizing is important for port velocity, which is based on the runner's size. A smaller cc port that flows 300 cfm will normally help the engine make more horsepower than a port that is, for example, lOcc bigger and flows the same 300 cfm." Burcham told us that the higher air speeds and velocity fill the cylinder better, which allows the engine to accelerate quicker and ultimately make more power.
The Brodix LH 210cc heads we sampled flowed 298 cfm at 0.500-inch lift and 317 cfm at 0.600-inch lift on the intake side. We didn't flow the ports at higher lift ranges as our application features a mild hydraulic camshaft that checks in at 0.560/0.570-inch lift. Those results are 2 cfm less than the flow numbers shown on Brodix's website. The difference is probably due to variations between the flowbenches.
Moving to the exhaust, our independent testing showed the exhaust ports flowing 217 cfm at 0.500-inch and 221 at 0.600-inch lift. Typically,
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