Most of the time, V6s are far behind straight-sixes as the inline engine offers more of a natural balance, simpler design and easier maintenance. There are not as many renowned V6s, but the car community is somehow more aware of the Alfa Romeo V6 'Busso' than any other six-cylinder of such type. What makes it so special?
thought by experts to be the best tuned engine in the world no wonder Cosworth showed interest in the famous Alfa Romeo V6 engine. Unofficially known as the Busso there are tons of iconic and legendary engines from all the corners of the world but when it holds its engineer's name, it is not just a story of an engine. It is known as the world's best-sounding V-6 and there isn't a Busso article not mentioning its glorious sound.
The man was called Giuseppe Busso and being an industrial engineer he spent his early days at Fiat. After leaving Fiat, he soon joined Alfa Romeo which saw great potential in the man. During the Second World War, he became unemployed. Back then and Enzo Ferrari wanted a new engine and asked then Alfa Romeo engine designer Gioacchino Colombo to build him a motor. He agreed to do it in secret and suggested putting Busso in charge of supervising the development.
Enzo got his V12. Colombo was from then on a full-tome employee at Ferrari and Alfa Romeo instantly invited Busso to return in 1948.
Giuseppe designed an Alfa Remote Twin Cam 4-cylinder which proved as a step in the right direction.
However, the Twin Cam could not provide enough power for more performance-oriented models and the company started thinking about a larger displacement engine.
Busso and his team would start working on it in the late 60s.
A near production-ready concept engine was finished in 1972 but unfortunately for Alfa and Busso the project had to be postponed due to an ongoing oil crisis.
The engine would wait over half a decade to finally be produced. Around this same time when Busso was at the age of 64, he retired in 1977.
But fear not, he had still been developing the engine for Alfa.
In 1979, the newly developed V-6 began as a 156 hp oversquared six-cylinder having SOHC heads.
12 valves and six individual carburetors Dell'Orto FRPA 40. Many features of the Twin Cam could be found in it: hemispherical combustion chambers, all aluminum construction, iron wet liners, a forged steel crankshaft and later the twin-cam setup. The beauty of Alfa's belt-driven SOHC was that the intake valves were directly pushed by the camshafts on top of them and the sodium-fitted exhaust valves were managed by rocker arms and small pushrods.
For this reason, the exhaust valves required tighter clearance on the buckets to work properly: 0.22-0.25 mm vs 0.45 mm on the intake side.
The engine had large 88 mm wide cylinders with a relatively short stroke of 68.3 mm.
Such an oversquared ratio is normally seen on high-performance high-revving engines like in Ducatis, Ferraris or Porsches as it favours a revvy character (besides other things).
But this was a road-going engine for the masses hence it was interesting to see that it was still strong enough at low revs and able to impress owners and the press.
While other competing brands were slowly getting into fuel injection, mechanical or electronic.
Alfa Romeo could not sacrifice throttle response and no injection system at that time could support ITBs, so they choose to go the carburettor away.
It didn't take long before the Bosch L-Jetronic electronic
fuel injection was released with a modernized engine in the Alfa Romeo 6.
This was the time when the engine was longitudinally mounted in the Alfa Remo 6, 75, 90 and the Alfetta GTV6 which actually had a transmission at the back as a transaxle.
A two-litre was introduced in1983 until 1987 and was meant as an entry-level unit made with both carburetors and fuel injection.
In 1985, the 2.5-litre was later upgraded by Autodelta Alfa's former racing department, with an increased bore and stroke.
They newly developed three-litre had 2939cc of displacement with unique carbs and cams making 176 hp in the GTV6 3.0 SA.
Only 176 examples with hard-built engines were made retrofitted from the original 2.5s.
Alfa liked the larger engine and decided to build their original three-litre 2959cc to be exact, to boost sales of the Milano in the USA, the European 75. It, too, featured the SOHC setup but used a slightly longer stroke of 72.6 compared to the 72 mm Autodelta engine.
The L-Jetronic was used instead and gave the engine the ability to make up to 210 hp in the spiciest trim the Alfa Romeo SZ.
The 3.0-litre was also modified for placement in a transverse engine bay for upcoming models like a164. The 164 introduced the famous chrome long-intake runners which were a necessary modification for a bonnet clearance. A special version of the 12V was a two-litre turbo. This one was sourced out of a 3.0 12V using 80 by 66.2 mm large cylinders.
The main reason for the turbo variant's existence was an Italian tax penalty on engine displacements above 2000 cc and thanks to forced induction it could provide three-litre's output with a torque-peak at 2100 rpm.
In 1993, a major revision was introduced with twin overhead camshafts now operating 24 valves in total.
The 12V was easier to change spark plugs in whereas 24V iterations require an intake plenum removal. Regardless of the higher service difficulty, the new engine was more eager for revs and made a high hp output. The first one was a three-litre in the 164 with 210 hp and 232 hp in the Quadrifoglio Verde, later followed by the Lancha Kappa and Alfa Romeo GTV. Then in 1996, a smaller 2.5 came to the world using the same bore and stroke dimensions of the SOHC unit. The only models equipped with it were the 156 and 166.
Its power ranged from 188 to 192 hp and it won the International Engine of the Year award in 2000.
The swan song of the Busso was a 3.2-litre. Initially introduced in a 147 and 156GTA, they both received a 250 hp engine and it was detuned to 240 hp for the 166, GTV and GT.
A 230 hp version of the 3.2 was used in the Lancia Thesis.
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As an honorable mention, there was a further tuning of the 3.2 by Autodelta
increasing the displacement to 3.7-litr and there was even a supercharged version of it. Then it was either 328 hp or over 400, all going to front wheels via an LSD.
For all Busso engines, the crankshaft was forged and fully counterweighted with nine weights. Connecting rods were also forged and interestingly an all were the same sizes for any displacement. They were merged to large cast aluminum pistons ranging from 80 to 93 mm in diameter and for the two-litre they were narrower than the rods. The two-litre requires a liner removal installing the piston from underneath and then reinstalling the whole cylinder inside the block. The engine is mechanically pretty solid and well built with not many design errors or failing points. The first turbocharged models had ancient engine management regarding fuel mixture control and were able to knock themselves to death even with a working knock sensor.
Later models in the 166 with an intake temperature sensor and an improved ECU brain were able to prevent a total engine failure.
The Busso engine requires a new timing belt every 60,000 km, regular oil changes and valve adjustments are needed in variants with solid lifters. It is known to consume gasoline at a rapid pace but people don't buy a gasoline Italian for fuel consumption.
There is a guy on Classic Alfa Forum who compared a 12V and a 24V block and they seem to be nearly identical making the 24 valve almost easy to retrofit into older longitudinally-oriented platforms. An interesting finding is that it is possible to use 3.0-litre 12 valve pistons with a 2.5-litre 24V crankshaft to lower the compression ratio making a more ideal combination for an aftermarket turbo. It could possibly be a non-interference engine, too. A major problem would be the oil pump, the pickup and the drive cog possibly able to be fixed with a dry sump setup and a spacer replacement for the cog.
Last but not least, there was one more engine somehow related to the Busso V-6. Between 1993 and1996, Alfa raced in DTM and had to use a production engine block with the same bank angle for the race motor. Hence for the 1993 season, the 60 degree aluminum design was used with a dry sump system and they four-valve setup, including titanium intake valves. The engine weighed only 110kg compared to the 170 kg heavy 2.5-litre SOHC and made 420 hp @ 11,800 rpm. A 1996 engine had up to 490 hp but it was a completely different unit that was allegedly loosely based on the PRV 90 degree V6 series.
This engine plays a symphony every time it gets into revs and its hunger for rpm is known to be insatiable. The whole story could not be more poetic as Giuseppe Busso died just three days after his engine ceased production forever in 2005. There are not that many iconic V6 laying around and Busso is deemed to be the greatest V6 engine ever.
