The Transalpine Formation

A closer look at the SM’s Maserati-sourced V6 engine. 

Alfieri’s production SM unit. (c)

Like most aspects of historical record, the story behind the development of Maserati’s 114-series 2760 cc V6 engine is dependent upon whose account one reads; the orthodoxy suggesting that the engine supplied to Citroën was a derivation of an existing Maserati V8 unit. However, its bespoke basis has been placed beyond doubt.

When the request from Paris came through, Maserati technical director, Giulio Alfieri took a pre-existing 4.2 litre 90° V8 unit from his workshops, and by effectively slicing two cylinders from the block, fashioned a 2.9 litre prototype engine. However, while the subsequent production engine may have shared the original unit’s included angle, it was in fact new from the ground-up and designed specifically to Citroën’s specifications.[1]

The 2.7 litre capacity was arrived at to ensure an adequate power/economy balance coupled to the fact that it would lie within the French government restrictions on engine swept volume, above which punitive taxes would apply. Alfieri chose to retain a 90° included angle, firstly because it aided packaging, both within the engine bay and around the engine itself and because it was a layout familiar to him. However, this was not an ideal included angle for a six cylinder engine, most V6’s employing a 60° vee – for smoothness of operation.

A primary stipulation from Quai Andre Citroën was for a compact and lightweight unit, physically no larger than their own in-line four. With the 114-series V6, the architectural layout chosen by  Alfieri allowed these strictures to be met. However, this brought forth a number of structural and operational compromises – one in particular proving something of an expensive error.

Owing to the 90° included angle between cylinder banks, it was prone to uneven firing intervals and a lack of smoothness at certain engine speeds. It was therefore decided to carry the counterweighting on the four bearing crankshaft and accept the uneven firing intervals. The major engine components; cylinder block, crankcase and heads were all aluminium pressure castings – the cylinder heads being interchangeable. Cast iron liners were press-fitted into the block, the flat crowned aluminium pistons giving a 9: 1 compression ratio.

Sufficient breathing was an important design priority; one advantage of the wider included angle being that it allowed additional space in the vee for ancillaries and in particular, induction porting. The V6 followed normal Maserati practice in that it employed four chain-driven overhead camshafts, the cylinder heads allegedly being designed in such a way so as to be capable of allowing for larger valves or a four-valve layout if necessary. There was also provision for a longer stroke version, bringing the swept volume up to 2965 cc.[2]

Induction was via three dual-barrel Weber 42 DCNF/2 downdraught carburettors, and in 114/1 specification, produced 170 bhp (DIN) at 5500 rpm. In mid-1972, a revised version was fitted with Bosch D-Jetronic fuel injection (114/3) for European markets, which saw maximum power upped to 178 bhp (DIN) with a slight improvement in torque. The same year, the SM was introduced into the US market with the 2965 cc unit (114/11), developing 190 bhp (SAE) on triple Webers, mated to a Borg Warner 3-speed automatic transmission. The complete engine, made up of 1140 individual parts came in under 140 kilograms, 25 kg less than the later PRV unit as employed by Peugeot, Renault et al.

Maserati 114-series V6. Author’s collection

Where the 114-series unit differed most notably from standard Maserati practice (and underlines its unique construction) is in its camshaft drive, which is mounted centrally, running the entire length of the block. In addition to providing drive for the camshafts (via three individual duplex timing chains), this shaft also powered the main hydraulic pump, water pump, alternator/generator, and air conditioning pump. On US-specification models, it drove the air-injection pump for the emission controls.

But it was the 114-series engine’s camshaft drive that was to prove its Achilles heel, more specifically the chain tensioning arrangement. With the key design work completed and prototypes built, the bulk of development and proving took place by Citroën engineers in France, much of it around the Mont Ventoux in Provence. A huge amount of development miles were amassed, the engine proving to be wholly satisfactory, which begs the question of how the issue failed to materialise.

Chronicler, Peter Pijlman suggests that Alfieri had warned the Bureau d’Études about the primary chain tensioner, but that his advice to use a stronger component was ignored. He states that Citroën’s rationale was that they had used this version extensively in the DS with no problem. However, this was a completely different proposition – a modern high performance engine, it being deemed “unfit for this type of chain tensioning” by former Alfieri cohort, Anacleto Grandi.

Author’s collection

According to Grandi, the gear teeth within the tensioner would degrade over time as the engine heated and cooled, causing the teeth to jump, ultimately leading to a meeting of valves and pistons. Thousands of engines failed in this manner, arriving back in Modena to be rebuilt.[3] It took some time for these problems to come to light, but once they did, it was a huge blow, to Citroën, to the reputation of the SM and to Maserati.

Nevertheless, Maserati technicians quickly discerned the cause and by employing a different tensioner design the problem disappeared. However, for the SM, permission to implement the fix was not forthcoming from Paris – the edict being to repair the engines but not to modify them. Politics once again reared its head and would be to both SM and Maserati’s detriment.

Author’s collection

One noteworthy development was that of a 1999 cc version of the 114-series engine which was produced for the Italian market to circumvent motor tax laws. Developing 159 bhp (DIN) at 7000 rpm, it was fitted to the Maserati Merak, but unsurprisingly proved no ball of fire. However, could it have potentially allowed for a cheaper, entry level SM?

A further (stillborn) development, was the fitment of the 114-series engine into a prototype Citroën CX.[4] By 1975, Maserati engineers, desperate to maintain the company’s viability, created what was known as Vehicle L, which had an adapted version of the V6 which could be fitted into the CX’s engine bay, using the same engine mounts.[5] It was evaluated by Peugeot management, but by that stage the game was up. Sochaux had their own ideas.

[1] Alfieri’s initial cut down prototype V8-derived prototype still exists in the Italian Panini collection. Source: Marc Sonnery.

[2] While the 3-litre unit was the largest capacity version of the 114-series fitted to the production SM, Maserati built a 3.2 litre version for their stillborn Quattroporte II model. [Source: Marc Sonnery]

[3] [Source: Marc Sonnery]

[4] A number of experimental four-cylinder versions of the 114-series were also made and fitted to prototype Citroen CXs. [Source: Marc Sonnery]

[5] There were apparently two prototypes, one with a transversely mounted V6, the other longitudinal. [Source: Marc Sonnery]

Sources and references:

Citroën SM : Jan P. Norbye
Citroën SM : Brian Long
Sa Majesté – Citroën SM : Peter I Pijlman/ Brian Cass
Citroën SM – Accidental Death of an Icon : Stuart Ager
Maserati- The Citroën Years 1968-1975 : Marc Sonnery

Author: Eóin Doyle

Co-Founder. Editor. Content Provider.

22 thoughts on “The Transalpine Formation”

  1. An excellent, if frustrating read, thank you Eóin. A known fault with a simple fix that was allowed to spoil what could have been an excellent engine. How crazy was that? It sounds like a much better alternative to the PRV V6, but Peugeot was committed to the latter, so Citroën had to tow the line. As to Citroen dealers letting the side down (again), that’s a depressingly familiar tale.

  2. Whilst knowing of the chain tensioner issue from my chats with the guys at BL Autos, I have not read enough previously to have know this level of background to the story. It always seems amazing to me how, once a design problem is known, management often seems to override the advice of the expert engineers they employ – a bit like certain politicians who keep ignoring the medical advice of learned clinicians regarding the spread of Covid-19; why would you do that, the implication being that you think you know better?

    There’s great irony (as well as frustration) in this story in that the whole point of the Maserati V6 was to provide a positive stand-out feature of differentiation for the SM, enabling Citroën to put to bed accusations of ancient and rather lumpen engines being out of place in its otherwise sophisticatedly engineered cars. Instead, the on-paper promise of the V6 came to be seen as the real-life Achilles heal of the SM. It makes me wonder if any Citroën really ended up with an engine which one would ever call truly worthy of the rest of the car?

    1. 2CV and Ami Super might be the only Citroens with engines worthy of the rest of the car.

    2. Dave – yes, I had those in mind as being potentially worthy, also those in the GS (I like horizontally opposed engines, and air-cooling too).

    3. The GS was underpowered for all of its life and early engines had significant durability problems. Opposed to you I don’t think air ccooling is a good idea, particularly not in a car that was brand new in 1970.
      Look no further than Alfasud for the engine the GS should have had.

    4. Again, fair point, and agree about the Alfa’s flat-four.

  3. Early SM engines had a spring loaded chain tensioner for the primary timing chain. The tensioner did not have enough travel to keep the chain on tension once the chain had stretched more than a very limited amount – letting the chain jump a tooth or two and this was made worse because the chain was not strong enough and stretched too much.
    The chain’s guide rail was made from folded steel and could wear away or break off.
    The irony is that a possible and common solution is to fit a better chain (IWIS instead of Renold) and use the hydraulic tensioner from the DS which is a straight fit because the SM engine already has tapped drillings for it. Also the much stronger guide rail from the DS can be used (think about that what you like).
    For the Merak engine Maserati used a completely different and much better but very complex hydraulic tensioner that can be retro fitted to the SM engine.

    1. @ S. V. Robinson
      Yes but the GS engine achilles heel was the belt that drove the cams!
      Not as foolproof as the 2CV.

  4. For all SM lovers with a big enough wallet, Gooding & Company is offering a special SM on 22 January in Santa Monica. Actually, there are two in the package, which makes it even more interesting.

    The record-breaking car has set several records in different classes. The builder has probably got to grips with the engine problem – if perhaps only for the short time needed.

    1. The many stories about this SM engine on DTW continually remind me what a dog’s breakfast it was.

      The brief from Citroen about physical size was surely not met with such girth. Then:

      1. The interchangeable heads imposed limitations, including having to drive the camshafts from both ends of the engine with resulting assymetric chain paths. The rear one is particularly inelegant.

      2. So why did they put the layshaft so high in the block when it needn’t to be if one looks at the cutaways. Or was it because the flywheel got in the way of driven accessories?

      3. The spark plugs were very far off centre in the combustion chambers. Jaguar managed better in 1948, and the ’50s Chrysler hemis better again. Always the limitation of two valve hemi heads, poor flame path length. At least this engine didn’t have a domed piston ruining the hemi shape completely.

      4. The exhaust valve seats had almost no nearby cooling water passage in the head, something I’ve never seen so disregarded anywhere else. Thank goodness for sodium-filled valve stems, one supposes.

      5. The included valve angle is so wide it looks like something from the 1930s with its far apart camshafts.

      6. A 90 degree V6 because those huge heads got in the way of the Webers if it had followed the proper Lancia 60 degree way, so now you have uneven firing impulses instead. Fan-tastic. Not.

      Maserati could have invented the split throw crankshaft pin 6 years before Buick for the 90 degree V6, but the thought never occurred. The PRV V6 repeated the sin, but in 1991 Audi said thanks very much GM and made a very smooth 90 degree V6, and has ever since. The original 90 degree V6 Buick and PRV engines have the excuse they were cut down V8’s. What was Maserati’s excuse again? Oh yes, induction.

      7. Various camshaft chain tensioner compromises documented by so much on the road experience. Not at all brilliant if it were that easy to fix by mere owners with imagination and talent.

      Another production engine came out at almost the same time as this alloy wonder, and pointed the real way to the future. The Cosworth BDA in the Escort RS1600. Duckworth wasn’t mired in the past. Four valve heads, tight dual camshaft spacing under a single cover, pent roof combustion chambers with central spark plug, all telegraphed to the opposition by the FVA in 1965 and DFV in 1966. Ignored by all and sundry, because who the heck was this bloke Duckworth, anyway? “It’s a racing engine, old man, not a touring engine design.” How wrong they all were.

      One can fantasize about a cheaper to make, smaller 60 degree V6 that didn’t vibrate, with more compact yet far superior heads, and decent exhaust valve seat cooling. Too bad Duckworth didn’t have an Italian surname, I guess. The Not-Invented-Here syndrome struck again. And would continue to for years, Toyota incorrectly claimed wide camshafts were the sporting alternative right up to the late 1980s in their Celica brochures.


    2. The C114’s camshafts weren’t driven from the end of the engine. Drive was in the centre of the cylinder bank, like 1-chain-2-3 and 1-2-chain-3. The intermediate shaft was set so high because it had to protrude over the flywheel and to keep the secondary cam chains high to allow tighter cylinder spacing and a shorter block.
      Italian engine designers adhered to old fashioned head designs for a very long time like the Lampredi four that didn’t get a squish band until it went four valve for series production in the eighties. On the other hand Alfa GTA/GT Am engines had very tight valve angles and two spark plugs for short flame paths very early.

    3. Keith Duckworth indeed showed the way, yet it appears that, in period, very few, except for some of his direct competitors in motorsports (Forghieri, Rosche) realized what he was up to. The thinking behind Cosworth’s 4-valve narrow angle combustion chamber with ‘tumble swirl’ combustion was not widely understood up to the early eighties

    4. Giulio Alfieri was a fine engineer in many respects, but it is well documented that he suffered (like so many engineers in so many different fields) from an excess of dogmatism. Also, like a number of his fellow senior automotive engineers (Issigonis at BMC and Fessia at Lancia for example) his overbearing personality, coupled with a ‘my way or the highway’ approach cowed both subordinates and management alike.

      Not that he set out to produce an inferior engine – who would? More that he operated according to the principles he believed were correct – very much an old fashioned, seat of the pants approach. One doesn’t imagine he spent his evenings poring over SAE papers, although, he may well have benefitted from doing so.

      Citroen’s knowledge base on engine design was clearly lacking – after all, why else would they go looking for an external supplier? Bercot was not only gripped with a nostalgic desire to further one of the Grand Houses of the automotive world, but was it seems, charmed by Alfieri and taken by his palmarés. Lastly, and in the final analysis, Citroen viewed the Maserati unit as Modena’s problem child, and largely washed their hands of it once Bercot left the company.

      Should Citroen have looked to an alternative supplier? Perhaps. But it wasn’t as if they were spoiled for choice. Alfa Romeo’s V6 was probably the most obvious – had it been in the frame. But it wasn’t. The PRV (regardless of merit) was not a factor, since Peugeot would have vetoed its use – as it is said to have done even after their acquisition of the double chevron.

    5. Thanks Bill for pointing out who actually invented the split pin/journal crankshaft (in 1977). I notice that Audi appear to hold some related patent(s) at least in Germany. I didn’t find any assigned to GM, perhaps because they’ve expired.

      I think this matter is a bit confusing to me because Ferrari had implemented a functionally similar solution for the 65° Dino V6 as early as 1962, Alfieri must have been quite aware that such a solution was possible. I am somewhat partial toward the triple-rotor Wankel theory perhaps because I vaguely recall reading those rumors at a very young and impressionable age.

  5. Was the cut-down four-cylinder version of the 114-series engine an inline-4, slant-4 or V4? Because the latter brings to mind a 1800cm3 two-stroke supercharged V4 Citroen experimented with at some point (the supercharger being driven by its own 200 cm3 four-stroke engine).

    It is pity the fix for the Maserati V6’s issues was denied and allowed to fester to the point of damaging the reputations of Citroen, Maserati and the SM.

    Guess the 2-litre Maserati V6 could have provided one way for an entry-level Citroen SM against the 130 hp 2-litre and 124 hp 2.2-litre DS Sport DOHC engines, the latter two likely being more useful in a DS Sport than the SM despite the 4-cylinder DOHC being under consideration for the SM during development.

    Apart from the addition of turbochargers, it is known what the differences were between the Maserati V6 in the SM Merak and the later Biturbo V6? Seem to recall reading one online account of De Tomaso finding one naturally aspirated 150 hp Maserati V6 displacing 2.5-litres to use as the basis for the Twin-Turbocharged Biturbo engine.

    The same goes with regards to the relation of the Twin-Turbocharged 3.2-litre V8 used in the Shamal. 3200 GT and Quattroporte IV with both the Biturbo V6 and original Maserati V6 engines (plus the experimental V6-based 4-litre V8 prototype engine in the SM and intended for the Quattroporte II).

    1. Maserati C114: two valves per cylinder, DOHC, chain driven cams.
      Biturbo: three valves per cylinder, SOHC, belt driven cams.

    2. Some say the Biturbo V6 was a completely new design while others claim it was based on or heavily modified from the SM/Merak V6, being simplified in some respects whilst enhanced in other respects including the addition of two turbos (plus the Hi Tech 6: 36 V6 prototype with 6-valves per cylinder).

    3. I suppose people can say whatever they want, but the two engines have literally *nothing* in common (besides a 90° angle, I suppose), making it essentially impossible for the Biturbo to have been developed from the 114. (They certainly developed turbo technology by turbocharging a 114—that prototype is also held by the Panini collection and actually displayed [unlike those mentioned above]—but that shouldn’t be misconstrued to mean that the Biturbo engine is somehow related to the 114.)

  6. Why didn’t they employ a split pin crank to solve the uneven firing order issue?

    1. Hello gooddog – I’d guess they’d be worried about loss of strength if they went down that route.

      I wonder if there was an element of ‘Not Invented Here’ among Citroën engineers about the engine.

  7. The PRV is the better engine. It had a lot more potential built in from inception. Unfortunately it was introduced at exactly the wrong time and into the wrong conditions (politics, economics) by the wrong management and marketing team.

    Try getting some decent power out of the Maserati engine and see how far you’ll get (the PRV in my 605 has 300bhp so far, John Lane got more than double that out of his PRV and WM were knocking on the door of 900bhp with theirs- although they did have four valves per cylinder for that). My engine runs with standard six-throw crank, standard block, standard sleeves and standard two-valve head castings. John’s was also on standard crank, two-valve heads and block etc., although he used US manufactured rods and pistons which are most easy to get for those domiciled in the US (he ordered 3/4 of a V8 set).

    There is just way too much monkey motion in the Maserati. Forget it. PRV is the better choice.

    1. Sorry JT, you may have a very well developed late-model example but for a customer of the 1970’s the PRV engine was dire. Never forget, the PRV was one of the nails in the DeLorean’s coffin, surely very high on the list of ‘cars cursed by its own engine’. A litttle like the 114, PRV’s asprations were for a V8, hence the 90 degree bank angle. If you look at the cars you could buy with a V6 in the 1970’s the PRV offered the least horsepower for your money. Citroen had Rally cars running the 114 on 270 bhp. Ligier had it up to 330 bhp and racing at Le Mans in the mid-seventies. When Jerry Hathaway got his Citroen SM up to 202mph at Bonnefille in 1985 you know this was not running 170 bhp. What Eoin does not tell you is that for a high-bred, aristocratic engine, the 114 is near-bulletproof. There is a shortlist of standard mods, including the chain tensioner, decent chains, solid exhaust valves (the sodium filled ones break, solid ones do not) and a slightly modified throttle linkage and it will go on forever. When I sold it, my car had done 120,000 miles and counting on the Reynolds chains I had fitted when I acquired it. I had the chains checked regularly, they were always fine. We should also recognise that for a timing chain to fail and detonate the engine, the driver must spend some time ignoring the hideous noises that it is making. Timing chains do not snap, they skip teeth; that’s the engine’s way of telling you to switch off. Do that straight away and the valves will survive. Expect a Citroen SM of the 70’s to be in the hands of a rock star who is less concerned with oil changes than they should be and it’s no wonder they had problems. What Eoin is also not telling you (yet) is that Peugeot were diametrically opposed to permitting Citroen from retaining its ‘Top French Car’ mantle justifiably earned by the startling DS and SM. This meant no V6 for the CX, even though the PRV would have worked just as well as the Maserati 114 in that engine bay. No, the Maserati C114 is no more fragile than any other high-performance engine of the time and arguably more robust than anything made in the Modena region for years to come. So why does the SM have a reputation of fragility? Surely it couldn’t be Peugeot justifiying their decision to kill the car? Could it?

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