If you were to attend any hi-performance engine building seminars or schools. Or the PRI show in Indy. You would find that none of the "Pro's" will use a gear drive on a street-strip SBC type motor.

Gear drives transmit all the vibration and harmonics from the lower end. Directly to the valve train. Computer simulations supplied by the big cam retailers. Show how the push rods amplify this vibration/motion to the valve springs. This causes the entire top end of the motor to vibrate like a tuning fork. Not good on already taxed valve train components..

According to those in the know. The best is a Jessel Belt. The next best is a double roller chain.

When asked why they still sell gear drives? "THE KIDS BUY EM" was the answer..