Written by Ray T. Bohacz
Jesel, one of the best competition valve train specialists to emerge in the past thirty years, owes much of its supremacy to extensive developing and testing of its competition parts. The test machine is a SpinTron. The parts being tested are principally roller tappets and rocker arms.
“Ten or twelve years ago when I first pressed the SpinTron into action,” says Danny Jesel, “my immediate response was one of shock—the racket it generated was incredible! I just wasn’t expecting the opening and closing of two valves to be so loud, and initially I thought something was broken.”
Once Danny Jesel became accustomed to the commotion, his next challenge was grappling with the phenomenon known as lofting. Lofting occurs when engine speeds increase, usually above 4,000rpm, causing the tappet and valve train components to lose contact with the camshaft each revolution. As a result the valves remain open much longer than camshaft designers had intended. Some race engine developers call it “controlled valve float.”