On July 24, 1998, about 1300 eastern daylight time, a Piper PA-28-161, N8258E, registered to Leading Edge Aviation Services, Inc., operating as a 14 CFR Part 91 instructional flight, crashed while making a forced landing onto a highway median near Tampa, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage and the student pilot was not injured. The flight originated about 40 minutes before the accident. According to the pilot, he had just completed a full-stop landing to runway 18 at Tampa's Vandenberg Airport, had back taxied and made a second takeoff, and was in his crosswind turn for a second landing, at an altitude of 500 feet agl, when the engine started vibrating and suddenly stopped altogether. The pilot felt his only alternative was to try for the highway off ramp median, and in doing so, collided with three construction sign standards. According to FAA inspector's statements, the sign standard collisions caused propeller, nose wheel strut, firewall, left wing, and upper left fuselage longeron damage. A postcrash engine run was conducted, and revealed a metallic knocking sound and exhaust blowing out the carburetor air inlet. Subsequent engine examination, with FAA oversight, revealed catastrophic internal failure. The oil filter contained pebblized metal pieces, and larger pieces of the No.3 exhaust hydraulic valve lifter/boss assembly were found in the oil screen. The No.3 exhaust valve pushrod had been peened and scraped for about 1/2 inch of it's length at the valve lifter end. The No.3 exhaust valve was stuck closed and appeared to have sustained extreme heat and burning. Additionally, the No.1 exhaust valve was stuck closed and the No.1 valve lifter was damaged. The Lycoming O-320 E2DA was designed for a 2,000 hour recommended time-between-overhaul, (TBO) interval. The time since overhaul for N8258E's engine was about 2,100 hours.