Its the internal clock that controls at what point the air/fuel mixture prepared by the engines carburetion will be introduced into the cylinders, and secondarily how much of it will be introduced.Ĭamshaft selection should have the same thorough thought invested in it as suspension design and setup do. Long-duration, high-overlap cam profiles create lumpy idles, little vacuum to operate the assist for brakes, and higher levels of noise than those with moderate duration. Regardless of a cams lift, duration dictates the attitude of the engine. Lesson number one: Duration is not like chocolate, exercise, and sex. Its all absolute, tangible numbers and science. Yet, engines never dip below 4,000 in a race, and T-A teams are rev-limited to 8,800 rpm.įor the vast majority of weekend racers and hot rodders, however, selecting the right camshaft for any application should not be perceived as a mystical, otherworldly task and should not emulate the aforementioned racing examples. Lobe separation angles are in the 104 to 108 range, helping to extend the powerband down for good torque to accelerate off corners.
SPLIT WITH CAM 350 PRO
He said that typically, Pro Stockers use up to 1 inch of valve lift, a little more than 300 degrees of duration at 0.050-inch lift, and 114 to 118 degrees of lobe separation, depending on the combination.Īs a comparison, Trans-Am racing engines, which must make power over a much broader range of engine speeds, have roughly 0.420-inch lobe lift, not more than 0.700-inch valve lift, 255 to 265 degrees intake duration, and 262 to 275 degrees exhaust duration. One cam manufacturer with involvement in racing told us that because Pro Stock engines have altered lifter bore angles and much less pushrod deflection, they can shorten up duration (from where they used to be five or six years ago) and still gain lift. When you get up into the Pro Stock drag racing and Winston Cup circle track strata, where a fraction of a percent in power advantage can put you in the money or on the trailer, cam specs are a very real issue of team security. Youd think national security was at stake, considering the way engine builders, racers, and some enthusiasts keep their high-power engines camshaft specs a triple-sealed, vacuum-packed secret.