Opus di Busso

Further to last week’s dissertation on the 1979 Alfa Six, we examine the contemporary reception to Giuseppe Busso’s Alfa Romeo 2.5 litre V6 unit, through the acerbic eye of LJK Setright.

The Busso V6 as fitted to the 1979 Alfa Six. (c) movitcars

Some engines arrive fully formed, others however, enter the world imperfect, but through a process of development and retrospective correction evolve to defy their early criticism.

A fundamental element of Alfa Romeo’s iconography was intrinsically linked to its engines, especially its pre-war thoroughbreds, those patrician in-line fours, sixes and eights which powered the carmaker into history books, not to mention the hearts and minds of all those with the blood of Portello coursing through their veins.

It was therefore an event of no little note on those rare occasions when Alfa Romeo introduced a new power unit, especially given that apart from the horizontally-opposed Alfa Sud unit, the storied Milanese carmaker had relied upon various derivations of twin-cam fours since the 1950s.

Of course what that statement conveniently ignores is the in-line six that powered various 2600 saloons, coupe’s (and a few convertibles) from 1962 to 1967, an engine which perhaps fell somewhat short of the high ideals, to say nothing of the expectations of the faithful.

The 1979 introduction of the Alfa Six was notable therefore, not simply because it represented the Biscione’s first attempt at an ‘ammiragila’ since the 2600’s demise, but more so because it also marked the debut of an entirely new, first-principles multi-cylinder power unit.

A six cylinder Alfa Romeo power unit seemed on paper at least to be a highly alluring prospect, so it was with some bemusement that the engine itself, designed under the supervision of Ing. Giuseppe Busso, was not only of a configuration not immediately associated with the marque, but contained within it, a number of technical solutions which, rather like the Jaguar V12 of 1971 departed noticeably from hitherto sacrosanct technical orthodoxies.

Alfa Romeo went to some lengths in 1979 to justify the adoption of a V6 layout for their new six, citing its connection to eminent engineer, Vittorio Jano, who was responsible for a number of legendary Alfa Romeo engines as technical director at Portello during the 1930s – although as LJK Setright somewhat waspishly pointed out in his June 1979 technical review for Car magazine, the engines Jano was associated with at Alfa Romeo were in-line units of six or eight cylinders.

Of course, following his dismissal from Portello in 1937, Jano went on to do what was arguably his definitive work at Lancia, and it was here that alongside Francesco di Virgilio, the first production V6 engine was developed for the Aurelia. Jano later went on to inspire the superb four-cam Ettore Zaccone Mina-designed V8 GP unit and latterly, the compact 65° Ferrari V6 which would (also) power Scuderia Ferrari to innumerable Grands Prix victories.

But if the connection between Alfa Romeo and the V6 configuration was, to say the least, tenuous, the engine itself was meritorious – albeit, this did not mean that some of its technical conclusions were viewed as being anything other than regressive, eliciting a theatrically raised eyebrow from Car’s resident engineering purist.

Arguably at least by the late 1970s, and certainly by the predetermined technical standards of Arese, the use of pushrod operated valvegear was not cutting edge technology, to say nothing of the employment of six individual carburettors, when fuel injection was already not only widely prevalent but preferable.

In his 1979 essay, Setright appeared at pains to debunk Alfa’s justification for their new engine, pointing out Alfa’s (correct) claims that their 60° unit was smoother running than rival units like the Douvrin 90° unit fitted to a variety of European rivals, but noting that while the Busso unit was narrower than a 90° configuration, it was also taller – albeit less so than an equivalent in-line engine.

However, (to paraphrase the late Jim Randle), despite the crankshaft not being the sort of thing one would ideally choose to have as a desk ornament, it was nevertheless a good deal shorter and torsionally stiff than that of a straight-six.

And if torsional stiffness might have aided the cause of smooth running, Car’s monocoled mutineer looked askance at the V6’s valvegear. Ingenere Busso either specificed or had imposed upon him the requirement to avoid unnecessary complication (perhaps bulk and certainly cost) and so the Alfa V6 employed single overhead camshafts operating at an included angle of 46 degrees 45 mins into part-spherical combustion chambers.

The larger inlet valves (41 mm in diameter) were directly actuated from the camshaft by piston-type tappets, while the smaller exhaust valves were actuated using short transverse pushrods and rockers – akin, LJKS suggested to pre-war BMW/ Bristol methodology.

Setright lamented the engine’s good but not brilliant inlet valve area in relation to the pistons (21.7%), and appeared to infer that the Alfa’s complicated valvegear would lead to an unnecessarily noisy engine – a matter for which he may not have been in error – albeit, the quality of the noise is often of more significance than the disturbance itself, and one thing which can be said of the Busso V6 is that in any configuration, the noise it left in its wake was a pleasing one.

Ing. Busso’s engineers went to the trouble of providing a sound spectrum analysis, showing the noise reaching the driver’s ears at 120 km/h – a road speed which the carmaker stated would only require 80 bhp and 3725 revolutions per minute to propel the car – and which appeared to back up Setright’s assertion insofar as the “loudest apparent noises are at 12, 18, 24, and 36 vibrations per [crankshaft] revolution, which are clearly harmonics of the basic mechanical and combustion pulsations.

In addition to the complex valvegear, LJKS also pondered whether the source of engine harshness might have been related to the “instant and uniform” combustion Alfa Romeo made much of in their launch material, Arese claiming that at 415.3 cc each, the V6’s cylinders were ideally sized for thermal and volumetric efficiency – a matter which dear Leonard refuted as nonsense, citing SAE papers by Honda as proof. Indeed he asserted that were the engine to display the former trait for which Arese’s PR representatives claimed, the V6 would in fact blow itself to pieces.

But if Setright was perhaps a little uncharitable about aspects of the design (and the manner in which it was presented to the press), he was nothing if not prescient in his perceptions – no more more so than when he observed; “What is easier to accept is the idea that the V6 may one day sprout four valve heads, in which case this valve-operating mechanism may begin to make sense.

Possessing a lower stroke to bore ratio than its putative rivals, it was clear from the start that Arese had bigger plans for the unit – clearly then, cylinders of 500 cc each were better still…

The 24 valve Busso V6 as fitted to the 164. (c) : automotive database

Setright concluded in a more consiliatory tone, noting; “A pinch of salt should suffice. Much better to attend to the opinions expressed by those who have driven the car and are competent to judge it: they seem to like it, and that makes it likely that the 2500 is a good car.

What we now know is that whatever the merits of the Alfa Sei as a vehicle or indeed an Alfa Romeo, Ingenere Busso’s V6, much like Mr. Hassan and Mundy’s Coventry-bred V12, evolved into very fine engine indeed – arguably perhaps, one of the greatest.

Author: Eóin Doyle

Founding Editor. Content Provider.

9 thoughts on “Opus di Busso”

  1. In a board meeting Giuseppe Busso once got accused that he was only able to design DOHC engines (what an accusation…). As a result he adopted the valve gear of an experimental engine designed for a joint development project with Bosch for his new V6 engine. This experimental engine had short horizontal pushrods for the exhaust valves and bucket tappets for the inlet side.
    This peculiar valve gear also allowed for an extraordinarily compact belt drive arrangement.
    Properly set up this valve gear is astonishingly quiet because the pushrods are very stiff due to their short length. The only problem can be premature wear because some batches of the engine were made with insufficiently hardened horizontal tappets and/or the design of these buckets doesn’t provide a proper oil reservoir for lubrication during engine start up and using the wrong oil (that doesn’t stick to the tappets) makes it run dry until full oil supply sets in after starting the engine.

    Ingegnere Busso insisted on using carbs on this new engine because it would deliver higher bmep than equipped with fuel injection – the torque curves of the carburettor vs. injection versions prove him right.
    The larger versions of this wonderful engine are mixed blessings and many Alfisti consider the 2.5 to be the best of the breed. The 3.0 and 3.2 are nowhere as smooth as the 2.5 and aren’t as willing to rev – everything is relative as there are few engines of this size as hungry to rev to and beyond 7,000 rpm. In the 3.2 there is very little material left between the bottom of the wet liners and the main bearing carriers so it’s close to the absolute maximum for a series production version of this engine.
    Early DOHC versions introduced in the 164 QV had a design fault in their cam drive making the belt jump a tooth or two every now and then resulting in expensive noises. This was only eliminated when the belt drive was comprehensively redesigned for use in the GTV 916.

  2. Now, why am I reminded of a Fulvia when I look at that pic of the camshaft?
    I still have a pair of cams and associated gubbins sitiing at the back of my garage.

  3. Speaking of the Jaguar V12, outside of the reputedly underpowered experimental prototype (developed prior to the AJ6) could a Jaguar V12-based 2.5/2.7-3.0-litre+ V6 have ever been a credible rival to the Alfa Romeo V6? And if not what would have been the best approach to take to make a V12-based Jaguar V6 viable?

    Know Jaguar had their reasons to dismiss DOHCs for the V12 (e.g. complex, large, heavy, noisy), with one opinion suggesting the V12 could have been improved by benefiting from a Honda style SOHC with rockers arrangement (allowing scope for a 48-valve version) though not sure how that would have been relevant for a hypothetical Jaguar V6.

    It seems Autodelta and others did managed to further enlarge the Alfa Romeo V6 to around 3.5-3.7-litres (with a few even stretching to 3.8-litres) and putting out around 300-328 hp.

    It is also interesting to note that Alfa Romeo did look at a 900cc version of the Twin-Cam engine for the Alfa Romeo Tipo 103 prototype as well as 750cc 2-cylinder version of the Twin-Cam engine in Project 13-61 (at a time when the Giulietta was still in the development phase) which preceded the Tipo 103 project.

    1. Jaguar intended to build an inline 6 from the V12. I’ve seen some old company advertising from the 1970s, although I’m not sure it ever made it to production.

      If you you were ever going to build a 6 cylinder from a V12, I don’t know why you would ever bother with a V6. Especially for Jaguar in the 1970s and 80s, where their cars were designed for inline 6s.

    2. Jaguar investigated a number of options before settling for a Slant-6 that eventually became the AJ6, a V6 being the most logical (despite the experimental prototype being underpowered) because it is basically an extension of the stillborn 60-degree V8 that was planned with the Jaguar V12 (and intended to both replace the XK6 as well as move Jaguar further upmarket), one which could have been put into production at very little cost in capital or development time.

      Could have potentially worked out well had the V12 been better developed and soon filtered down to a related 60-degree V6 capable of rivaling the Alfa Romeo V6, however as the V12 was such a V6 would have probably been more suited for an XJ Junior model as opposed to a worthy XK6 replacement.

    3. We have been around the houses at least twice on this one, I seem to recall.

      Jaguar did build an experimental 48-valve version of their V12 – as far as I can gather it was handed to TWR, who built a series for their joint Group C racing programme. One of these engines resides in the prototype XJ220, itself a permanent resident of Jaguar’s Heritage collection. In addition, a number of twin-cam V12 units were made during the mid-60s – ostensibly for the XJ13 programme, but a couple found their way into experimental Mark 10 saloons, which provided rather vivid performance.

      The slant six derived from the V12 was adjudged to be okay, but it lacked swept volume and given the type of cars Jaguar was making, would have proven inadequate. The lack of performance derived from the 2.9-litre AJ6 is ample testament to that. A V6 derived from the V12 ought to have been relatively easy to achieve and could, I would assume, have been capable of being made on the same transfer line as the larger unit. However, it would have suffered the same issue – even with a 3-litre capacity, requiring expensive solutions to provide a competitive power output.

      Why did they not consider a V6? Engineering orthodoxy I assume, not to mention BL politics, which were no small matter at the time AJ6 was conceived. However, Jim Randle did suggest that a V6 layout would have been preferable for AJ6 in retrospect when we spoke in 2016. Of course another rationale was that they genuinely believed they could alleviate the inherent imbalances of the 60 degree V8. This was achieved, ( I’m reliably informed) but much, much too late.

      However, As I also pointed out in the past, a 2.7 – 3.0 litre Jaguar-developed V6 would have been a very useful power unit for the group as a whole and could have supplanted the Rover/ Buick V8 in SD1, and perhaps obviated the requirement for Honda’s V6 unit for the 800 Series.

      But surely we aren’t simply going to discuss Jaguar engines in the (virtual) presence of Ing. Busso? Where are our manners?

    4. Potential uncouthness aside, the Alfa Romeo V6 eventually the benchmark from which other (existing or hypothetical) V6 engines are judged, whether it could have been doubled up for a truly flagship Alfa Romeo (and GT coupe – fuel crisis notwithstanding) in the same way the Jaguar V12 could have been halved is another subject.

  4. LJKS must have had a fit with the 2.5 litre Honda C Series engine that appeared in the Legend in 1986. I know I did when I got to inspect a cutaway one when even we in Nowheresville used to have an annual car show. Not only did it have a similar pushrod arrangement as the Busso to run the exhaust valves from the SOHC but twice as many for good measure, and it was a 90 degree V6 with one of those warped-up cranks with offset throws to give even firing, as Buick had started and the gutless PRV engine finally adopted. Elephantine in physical size as well, that first V6 Honda, the most complicated piece of nonsense cylinder head ever designed to my mind that prompted the question – why? I could go and drag out all my old mouldy CARs and find out if LJKS bothered to mention it, but after those earlier cutting remarks on the Busso design, perhaps he was discreetly quiet about its layout being a Honda man, so I won’t bother.

    One thing’s for sure, the Alfa slayed the Honda engine despite the latter’s 24 valves. Never read a bad review on any Alfa with any version of the Busso V6 – it dominated the car it was mounted in. Just one of those rare occasions where things turn out right – I’m yet to be persuaded that the Jaguar V12 was ever great – when people can substitute a Chevy V8 smallblock and the result is better in every way but smoothness, something wasn’t quite right in the first place.

    1. “I’m yet to be persuaded that the Jaguar V12 was ever great …”

      I think that is right. One of the things I am increasing able to understand is the importance of swirl and tumble of the intake charge for part throttle low rpm efficiency, detonation resistance etc. , especially with port fuel injection. All the fuel gets dumped on the intake valve and in-cylinder air motion is required to mix it. Swirl and tumble do that mixing more completely.

      One thing Jaguar got unlucky on the V12 was, with a SOHC and the valves inline and straight down into the cylinder, there was almost no inherent swirl or tumble in that design. With any pushrod inline valve engine, the port flows in at an angle and significant swirl is automatic – it would probably be hard to not have it.

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