The first TC-engine was presented in the Motor Show of Turin in 1966 as the power source of Fiat 124 Sport Spider. The engine was created by the ex-Ferrari engine design genius Aurelio Lampredi, and it caused a sensation immediately when it was presented. The structure of the engine was many years ahead of its time.
The four-cylinder engine had aluminum head and two over-head camshafts (DOHC) which were driven by a toothed belt. The camshafts lift the valves directly, without using any rockers or similar moving parts. On the top of the valves, there were valve buckets containing replaceable shims for adjusting the valve clearances. This kind of a structure is very common on modern automotive engines nowadays, although the number of valves per cylinder has increased from two to four. The engine had relatively long stroke compared to bore diameter (bore 80mm, stroke 71.5mm) which means short combustion time and increased torque.
Because of the engine's structure, the combustion chambers could be made hemisphere shaped, and intake/exhaust ports correctly designed. Some rare models of the engines in the sixties were equipped with Hemi heads, but the most of the heads used on production engines were poorly designed.
Therefore, the TC had superior power and fuel economy compared to its competitors of same engine size. The first 1438cc (88cid) TC made 90bhp DIN (100bhp SAE) using lousy CR of 9.8:1, which can be regarded as a good result even when compared to the engines of present time. 1608cc and later 1592cc, 1756cc and 1995cc versions of the engine were presented later, and those were at production until 90's with subtle modifications.
The most significant modifications were done in the 70's, when 80mm-bore models (1438cc, 1592cc and 1608cc) were replaced by 84mm-bore 1585cc engine. The other change was in 1986, when the intake- and exhaust ports were changed opposite. This was done to fit the engine better to the cars with transverse engine layout. The 16-valve version was presented in 1989, though Abarth had used 16v heads on the engine earlier - in the motorsport versions of Fiat 131 and Lancia 037, for example.
The TC is one of the most successful production engines used in racing in the history. As an example can be mentioned several World Rally championships. Fiat 124 Spider Abarth, Fiat 131 Abarth, Lancia 037 and Lancia Delta Integrale were equipped with this fabulous engine. 9 rally manufacturer's championships were won with these engines.
In production cars, the engine was used in several Fiat and Lancia models.
If one want to use the engine for tuning or racing purposes, it is advantageous to purchase the book "Modifying and Tuning Fiat/Lancia Twin-Cam Engines" (ISBN: 0-947981-98-5) by Guy Croft. This is really excellent pack of information, handling about everything that can be done with the engine. TC engines are quite cheap when obtained from scrapped cars. The car models to look for are listed here.Links: