Hornish puts new Chevy on top of the pile.

In a remarkable debut for the new Chevrolet Gen. IV engine, defending IRL Champion Sam Hornish Jr set the fastest time of all during Friday's two practice sessions for Sunday's Firestone Indy 400 at the Michigan International Speedway.

Hornish Jr jumped out of the blocks at the fast two-mile D-shaped oval, setting a fastest time of 32.1977secs (223.618mph) during the first of two practice sessions, which would remain the best lap of the entire day despite several teams attempting to draft and run in packs during the second session.

The 2001 and 2002 IRL Champion had tongues wagging throughout the day as the engine designed as a joint effort between Chevrolet and Cosworth proved to be more than a match for the previously dominant Toyota and Honda units.

Even though Hornish Jr reported his Panther Racing Dallara-Chevrolet wasn't performing well in traffic during the second session he was still able to post the second fastest time in the afternoon (32.3722secs) behind Scott Dixon.

Dixon's afternoon standard of 32.3605secs (222.493mph) was good enough for third on the combined practice charts behind Hornish and the ever-consistent Kenny Brack, who set a best time of 32.2894secs in morning practice.

Fourth fastest on the combined charts was Kansas winner Bryan Herta in his #27 Archipelago/Motorola Dallara-Honda while Dixon's teammate Tomas Scheckter rounded out the top five.

Alex Barron showed once again that he would be a force to be reckoned with during Sunday's Firestone Indy 400 as he capped off a typically fast and consistent day in sixth position on the combined charts in his Mo Nunn Racing G Force-Toyota.

Behind Barron, Helio Castroneves, Dan Wheldon, Al Unser Jr and Tony Kanaan rounded out the top ten with Kanaan unhappy with his practice speed for the second week in a row.

Even though Hornish Jr has been the fastest Chevrolet powered driver at almost every race this year, the gulf in performance between the new and old GM units was clear to see as the remaining five Chevrolet teams languished roughly five mph slower than the Panther Racing man at the bottom of the timesheets.

Team Menard's Vitor Meira, who hopes to have the Gen IV. Engine for the next race, was 17th overall with a best time of 32.8296secs with Buddy Rice 18th, Sarah Fisher 19th, Buddy Lazier 20th and Robbie Buhl 21st.