The Additional Sessions Judge acquitted six persons, and convicted D Ramachandra Reddy, Ravindranath Reddy, Subbireddy and Mangali Krishna.
Krishna, of Pulivendula town, is allegedly a close follower of Kadapa MP Y S Jaganmohan Reddy.
The four were sentenced to five years of rigours imprisonment and a fine of Rs 3,000 each.
Ravi escaped the suitcase bomb plot, but was subsequently gunned down in January 2005 allegedly by associates of gangster Gangula Suryanarayana Reddy alias Suri.
According to the prosecution, the main accused, Chalapathi, was caught with the suitcase bomb during a police checking on March 19, 2001 in Anantapur town. That led to the arrest of others.