We return to our analysis of the 50-year old Austin and Fiat contemporaries with a look at their engines. One was the work of a revered racing engine designer, the other was cobbled together by two capable backroom boys under the eyes of an unsympathetic boss.
On paper a conservative design, the Maxi’s E series engine turns out to be downright odd in its execution. It evolved from a 1300cc prototype with a belt-driven overhead camshaft, one of many experimental designs being developed in the West Works at Longbridge. Long-serving engine designers Eric Bareham and Bill Appleby were handed the task of reworking the inchoate power unit into an engine suitable for BMC’s new mid-range car.
More capacity was needed, so it was bored out to accommodate 3 inch pistons, leaving no space for waterways between bores or any further outward expansion. Issigonis vetoed belt drive for the camshaft in favour of a traditional single-roller chain, on the reasonable grounds that belt technology was new and unproven at the time.
Morris and Wolseley had built overhead-cam engines in the inter-war era, and there was also – for a couple of difficult years – the MGA Twin Cam, designed under Gerald Palmer’s watch. However, the E series was BMC’s first volume-production OHC unit, and therfore an undertaking not to be taken lightly.
The end result was unadventurous and compromised – more like an improved version of the 1952 BMC A series than a challenge to the best European and even Japanese designs of the time. There was limited opportunity taken of the freedoms offered by an OHC design; the valves are in-line, and directly actuated by the camshaft through inverted bucket tappets. The porting is reverse-flow. As all ports are on one side, there are restrictions on space and the layout imposed long inlet tracts, and much shorter tracts for the exhaust valves.
Most significantly, there is no convenient means of adjusting valve clearances. When required, it is a camshaft-out and shimming-up job. By 1968 the British automotive world was familiar with OHC engines from Jaguar, Rover, and Hillman, and also aware of the laboriousness and potential for catastrophe the tappet adjusting process entailed.
GM took up the challenge, and Vauxhall’s 1967 OHC slant-four had a clever screw-adjustable wedge system for adjustment. The 1970 Ford OHC “Pinto” engine had finger rockers. BLMC merely claimed that “once set, the adjustment usually lasts the full period between top-end overhauls”.
In 1485cc form, the engine was mildly undersquare (76.2mm x 81.28mm, or Imperially 3.0” x 3.2”) but far enough adrift of the prevailing short-stroke orthodoxy, to require something of an apologia. Edward Eves in Motor 24 April 1969 wrote:
“So much has been said about oversquare engines in past years that there is a tendency to regard any other type as out of date. However recent research in into objectionable exhaust emissions has shown that the small combustion chamber that goes with bore to stroke ratios of less than one gives low emissions, because of the small area of the quench surfaces.
It is significant that one of the latest engines to come from America (regrettably not named) is a long-stroke type. (Quench areas are the parts of the combustion chamber which stay cool enough during the combustion period to retain wet fuel, which is carried through into the exhaust). The Maxi head promises to be good in this respect because such areas are small and the head tends to run hot; low emissions mean that most of the charge is burnt, with consequential beneficial effect on fuel consumption.”
All of which is as may be, but it does not explain why early E series engines needed 5 star (100 octane) petrol, despite a not particularly high 9.0:1 compression ratio.
The E series’ in-line valves are inclined from the vertical to maximise valve area, to create what is described as a “pagoda”combustion chamber. The effect of the angling of the valves is to distort the sectional shape of the traditional BMC-Weslake kidney shape chamber. It was claimed that the deepening at the ‘belly’ of the kidney promoted turbulence and improved combustion.
There is a feeling that BMC’s engineers Appleby and Bareham stuck with what they knew well and adapted it as necessary. The E series was reasonably efficient, but was never developed for high performance use. Apart from the compromised top end design, the cylinder head was cast iron rather than aluminium alloy and the bottom end was weak – deliberately so, as it could depend on the gearbox in-sump casting for strength, allowing a reduction in weight and material use.
The E series’ five bearing cast-iron crankshaft had only four counterweights, and narrow bearings imposed by the closeness of the bore centres, and a Holset torsional vibration damper was fitted. The Issigonis-decreed need for a six cylinder E series restricted the engine’s width, needlessly as it turned out, as the assumption was that the six cylinder ADO17 would have a side-mounted radiator and engine-driven fan. In production a front-mounted radiator and electric fan were used for the transverse E6 installations.
Read between the lines and everywhere the story is of a compromised, cost-cut engine. The E series was not a disaster for BLMC, but in every aspect of its design it was a missed opportunity for a company which had not introduced an all-new engine since 1954.
With the celebrated engine designer Aurelio Lampredi as its parent, the 128 engine should have been outstandingly good, and for the most part it was. The proviso is that it was very much built down to a price, albeit with considerable ingenuity.
The first, 1116cc, variant was extraordinarily oversquare, with 80 x 55.5 bore and stroke dimensions. When more capacity was called for, the bore was further increased by 6mm to achieve 1290cc. The short stroke allowed an inherently strong five-bearing crankshaft, so all components could be produced by casting rather than the costlier forging process.
The design of the die-cast aluminium head is unambitious, but clever and appropriate.
Giacosa’s ‘123’ studies featured a three cylinder engine with a crossflow head with inclined valves operated through finger rockers by a centrally positioned overhead camshaft, an arrangement used by NSU, Lloyd, BMW and Glas. Constrained by costs, Lampredi opted for in-line valves inclined at 18 degrees to the vertical, and thankfully parallel, unlike the “knock-kneed” arrangement of the Maxi.
Like Austin’s engine, the 128’s camshaft operates directly on inverted bucket tappets. The refinement Lampredi carried forward from the 124/125 twin cam engine is a simple means of adjusting tappet clearances with the camshaft in-situ by inserting hardened steel ‘coins’ into recesses at the top of the tappets, with only an inexpensive valve spring compressor tool and a modicum of skill required to perform the operation.
The valve diameters of the 1116cc Fiat engine are only slightly smaller than those of the 1485cc E series. (Inlet 1.5” / 1.42”, Exhaust 1.22” / 1.2”)
The 128 combustion chambers are wedge-shaped and compact in size, following the principles established with Fiat’s older ‘100’ engine. However the squish area – the “flat face “ of the circular area surrounding the combustion chamber – is actually slightly concave to improve turbulence and scouring.
There is similar attention to detail in inlet tracts, with a constant diameter of 25mm and a gentle curvature at the approach to the valve. A toothed belt drove the camshaft – Fiat had successful experience of this with Lampredi’s twin-cam 125 engine. Even in its first 55bhp form, the engine was highly regarded, the strongest criticism being of the level of engine noise. Perhaps it was a cultural matter – Italians like to hear their engines, northern Europeans want to suppress the cacophony.
Like much of the 128’s engineering, Lampredi’s engine appears simple, but reveals purity of principle and an ingenuity which made the end product both cost-efficient and a joyous experience.
“Joyous” is a word never applied to any aspect of the Austin Maxi, but its E series engine is at least worthy. Eric Bareham and Bill Appleby were highly experienced and able engineers, but were frustrated in their ambitions by their master’s peculiar agenda. It really does seem that Issigonis saw engines as another necessity which had to be packaged, no different to a battery or heater.
With more freedom, Bareham and Appleby could have made something far better, rather than an engine compromised from its very inception. To their credit they worked tirelessly to de-bug the E series in the pre-production period, and were largely successful – the engine was reported to have lower warranty repair costs than the A or B series units.
To their discredit – or that of Issigonis – the engine was a fleet manager’s nightmare, with no easy means of tappet adjustment, and its demand for five-star fuel. Both of these failings were easily avoidable, but somehow nobody bothered.