Straight Eight – The Dilettante’s Viewpoint

The in-line eight cylinder petrol engine has receded into history. It has powered some of the great cars – the Alfa 8Cs, the Mercedes 300SLR, the Duesenberg SJ and the Bugatti Type 35, but its last appearance in a production car was in the early 1950s, in the finely named Packard Patrician.

The reasons for its disappearance are pretty obvious. It is not the greatest packaging solution and, with all those stresses and temperature variations laid out in a long line, it presents a whole series of engineering problems. Why bother when a V configuration is easier? For anything that has to be made to a budget, that is probably a reasonable attitude to take but, for some of us, the engine has a hugely exotic attraction, highlighted by its very impracticality.

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You should never actually make a glass topped table from a car engine, but a great car engine should look well enough to be misused for such a purpose. An in-line eight will never be the most efficient engine out there, but then neither will a Swiss watch be the most efficient timepiece. As it finally gets through to manufacturers and customers that ultimate performance is no longer a worthwhile goal, since the ability of today’s cars long ago outstripped the goodwill of today’s roads, they will need to cater to other sensations. That might be the purr of an electric motor, taking us at a regulated 30kph to and from our workplace but, assuming that the rich will always be with us, there will still be the call for something more profligate.

As people get older, they get to appreciate things more – or so I’m told. They savour things more and appreciate the subtleties, so why can’t this be the case with cars? The Veyron’s W16 is hugely effective for what it has to do, but it is hardly a thing of nuance. A finely engineered, smooth-running straight eight and the fine, long-nosed grand tourer that could be built around it would be though. An engine that, even if you were stuck in a 30 km tailback on an Autoroute, would still give you a tingle each time you pressed the throttle and urged it to move you forward a few hundred metres. In my imagination, I hear it now.

9 thoughts on “Straight Eight – The Dilettante’s Viewpoint”

  1. The straight 8 holds a similar fascination for me too Sean and the version in the Duesenberg is an automotive delight. In engineering terms the straight 8 is the button fly to the v8’s zipper- once presented with the better solution, why return to the difficulties of the former?
    Aside from balancing issues, which can be easily sorted by counter-weighting one problem with a long engine is mitigating angular momentum. Essentially you are trying to keep a long shaft not acting like a torsion bar- the shorter the shaft the less the effect and the smaller in diameter it needs to be. In low revving engines you can make the shafts (think cam and crank) greater in diameter to compensate without becoming excessively large but as the revs increase it is like trying to stop and start a licorice strap. Notice in the Alfa 8C above that the drive for the cams is centrally located so that the engine is acting like a pair of 4 cylinder motors.
    The forces imposed on these long shafts also have to be contained by bearings to make them work and each time this is done there is a loss as the energy from the rotation is dissipated as heat through the bearing.

  2. Mark. Although I greatly admire Jano’s Alfa engines, and I concede that the split camshaft was a clever and good looking solution, I have to say that it does disguise the sheer, indulgent length of an eight cylinder, which is a pity. The Duesenberg is a far grander engine, even if it isn’t a greater one (though it’s certainly as great a one). The pity is that modern technology and metallurgy could easily overcome the problems you mention. Incidentally, someone recreated an 8C Alfa many years ago by combining two Alfetta (as in 70s saloon, nor 40s racer) engines. I read a Setright test of it and he seemed to avoid mentioning the engine, so I suspect it wasn’t altogether successful. But come on, someone must be interested in doing it.

    1. Sean. The problems could be overcome, but the resulting engine would not be as pleasant as you’d hope- low revving with little power output and low efficiency. Again, the length makes it more difficult to keep the mating surfaces (block and head) flat while resisting the forces generated by combustion. There aren’t any positives in making the straight eight (in-fact it may even be better balanced as a straight nine) other than the romance of a long and unusual engine. I’d be interested in making it, but you couldn’t possibly sell it.
      Length is gratifying but not everything Sean, some people like short little things that are very earnest.

    2. Mark. You make the button fly analogy and people still use button flies (not me, I forget too easily). And they buy very expensive Swiss Watches.

      I’d never expect it to be the epitome of power (though if it was good enough for Stirling Moss in the Mille Miglia) and fuel consumption would be in the ‘if you need to ask …’ category. But my attitude is that the sheer impracticality of it would be the very selling point. Based on 11 units a year.

  3. Sean. So we agree that the engine is possible yet impractical what car would you suggest would accept the “ST8” (your name works so well as the nomenclature, it’s impossible to resist)? I nominate the Mercedes SLS as there seems to be plenty of room in the engine bay and it would be entirely appropriate, but that car is too ugly to accept a beautiful engine. A Ferrari FF would be possible but its V12 is only bettered by a V16, and would be better than the ST8.
    I think the best solution would be a Morgan. Their buyers expect unreliability an inefficiency and they probably couldn’t make more than 6 per year so it’d be perfect. I’ll design and build the prototype, you convince them to carry the warranty claims.

  4. Mark. Your suggestion of a Mercedes is certainly good, linking back as it would to the 300SLR. However, although they were actually mainly straight sixes, as an inspiration I have in mind the French streamliners of the 1930s, in particular the Talbot Lagos of Figoni & Falaschi or the Saoutchik Hispano Suiza Xenia.

    Not that I’m thinking retro, more imagining how these shapes would have evolved over 70 years if austerity and technology hadn’t put an end to such coachbuilt fantasies.

    I totally accept your point that the ST8 is outgunned by V8s, 12s and 16s, probably even V6s. Except in elegance and exclusivity. If we can just persuade the very rich to concede that, generally, their driving skills are as mediocre as those of the rest of us, and that they actually never really use anything like the performance of their uber machines, then they could learn to love, even to lust after, the ST8.

  5. Although, on a Spinal Tap level, I am almost tempted to up my ambition to an ST9. And, on a related subject, has anyone else ever produced an in-line 7?

  6. Sean, I’ve done some searching and when considering the ST8 (“so smooth, so long”) it will be better balanced than a four cylinder if the timing is set to mirror pistons 1 and 5, 2 and 6, 3 and 7, 4 and 8- at least around the centre of the block between cylinders 4 and 5 (looking from above the engine looking down the bores). This is based on there being a power stroke an the cylinder every 720 degrees of crankshaft rotation, so in a straight 8 there is a power stroke in one cylinder every 90 degrees. These mirrored power strokes thus cancel its mated torque reaction in the opposing cylinder. This is part of why a straight six is so smooth, but it has the added benefit of having all forces balance out as the crankpins are arranged in a beautiful cloverleaf pattern. Therefore a straight nine (“ST9 -extra length, extra fine”) would lose the counterbalanced power strokes over the ST8, but would retain the well balanced cloverleaf pattern crankpin arrangement of a six. An educated guess I’d say the nine would be better balanced overall.

    I can’t find a straight 7 that has been used for cars, no.

  7. There is a test of the 300SLR ‘Uhlenhaut’ Coupe by Andrew Frankel in this month’s Motor Sport. His description of the sound of the desmodromic valved straight eight suggests that it is awesome, but not melodic. Whereas Moss had an open cockpit to disperse the sound on the Mille Miglia, the coupe has a closed one to intensify it. It’s certainly not lacking in power and the driving of it, particularly since you straddle the propshaft, legs apart sounds memorable, to say the very least. Also, although there are similarities with the 300SL Gullwing, the look of the Uhlenhaut is, ironically, more elegant. With its wrap around rear window, softer curves and fared in headlamps, it probably looks more Italian than the SL, which is unmistakably a Mercedes, but it is undeniably an extremely fine looking car. Not my refined Grand Tourer though.

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