Complex sentence: Designed in 1949 and raced until 1954-55, it produced at 12,000 rpm, although test figures from Rolls-Royce suggested that the engine would be able to be run at up to 14,000rpm.
Split into simpler sentences: Designed in 1949 and raced until 1954-55, it produced at 12,000 rpm. Test figures from Rolls-Royce suggested that the engine would be able to be run at up to 14,000rpm.