Idle is smooth, but you can hear the difference in the exhaust sound that the cam makes under acceleration. A noticeable gain in low end torque and acceleration on my 1977 AMC 258. I have all stock bores and journals, just had the cylinders honed and the head milled .030. Change the oil and filter after the initial 25 minute break in, then at 100 miles, and again at 500 miles. Normal changes after that, and be sure to add a zinc additive with every oil change since modern oils don't have enough and flat tappet engines need it.