|Triumph Spitfire Mk3|
The 1147 cc engine was replaced with a bored-out 1296 cc unit (the bore increasing from 69.3 mm (2.73 in) to 73.7 mm (2.90 in), stroke retained at 76 mm (3.0 in)), as fitted on the new Triumph Herald 13/60 and Triumph 1300 saloons. In SU twin-carburettor form, the engine put out a claimed 75 bhp (56 kW), and 75 lb·ft (102 N·m) of torque at 4000 rpm, and made the Mark III a comparatively quick car by the standards of the day. Popular options continued to include wire wheels, a hard top and a Laycock de Normanville overdrive, and far more relaxed and economical cruising at high speeds. The Mark III was the fastest Spitfire yet, achieving 60 mph (97 km/h) in 14.5 seconds, and reaching a top speed of 95 mph (153 km/h). Average fuel consumption was improved slightly at 33mpg. The Mark III actually continued production into 1971, well after the Mark IV was introduced.
On 8 February 1968, Standard-Triumph General Manager George Turnbull personally drove the 100,000th| Triumph Spitfire off the end of the Canley production line. More than 75% of the total production had been exported outside the UK, including 45% to the USA and 25% to mainland European markets.
Starting in 1969, however, US-bound models had to be changed to comply with new safety/emission regulations; models produced after 1969 are sometimes referred to as "federal" Spitfires. The changes included a slight decrease in power (68 bhp) due to emissions control, the instrument panel was moved in front of the driver, and new seats were introduced with integrated headrests to help against whiplash. Also the wood dash was replaced with a matte black finish.