N.B. —Opinions expressed are those of our Correspondents and “Motor Sport” does not necessarily associate itself with them.— Ed.
Mini v. Imp
I strongly agree with the Mini v. Imp observations made in the November issue (name and address supplied), Perhaps Hillman Imp enthusiasts are sensitive to the apparent tendency to “knock” this car in the Press and elsewhere, but many readers will share the view that the Imp has received more than its legitimate share of criticism. I was amongst those who became intrigued by Imp engineering and decided to buy. Although oversize for this car (6 ft. 4 in.), I took delivery in August 1964 with the intention of enjoying a few months’ driving before getting a car more closely in line with family requirements. After thorough and restrained running-in, my Imp was driven hard for 10,000 miles during nine months’ ownership. My views and experiences may be of interest :
Faults on Delivery;
None, except “balanced” wheels grossly out-of-balance.
Faults in ServIce,
1. Gearbox; At 5,000 and 10,000 miles minor faults in otherwise excellent box. Jumping out of 3rd on overrun, roughness on quick 3rd/top changes.
2. Exhaust valve; One valve burnt badly at 10,000 miles; most likely from incipient fault, since remainder in good condition. Auto-choke reputation led to incorrect initial diagnosis of cause of rough running. (On the whole choke worked well for me, engine being notable for no-hesitation pulling from cold in all weathers. I was nevertheless suspicious about mixture strength at times.)
3. Flasher cancellation; Failed at 6,000 miles.
Rootes most helpful in dealing with the aforegoing shortcomings. Water pump and carburetter replaced for latest type although both operating satisfactorily at time.
With the seat frame back dropped 1 1/2 in., I found the driving position comfortable for up to four hours’ continuous driving. For me, layout of minor controls was near ideal, with most requirements at finger-tip range. I should have liked the flasher stalk to have moved in the same relative direction as the horn stalk. (Latter too embarrassingly “Noddy” to he usedl)
Wipers satisfactory for tall driver but my washers frequently blocked with residue in system from purchase.
The heater is simple and effective. although the temperature control lever is over-sensitive.
On the Road
I found the Imp a delight to drive under all conditions except in high winds, when the car proved a “pig” to keep on a chosen course.
Combination of smooth and direct foot controls, quick precise gearbox, light and accurate steering gave me great pleasure. With tyres regularly at 20 front and 32 rear (C41), handling was entirely predictable, not least during fast cornering. When eventually the rear end moved, the breakaway was gradual and easily corrected. Cornering performance in the wet was undiminished and its behaviour just as gentlemanly. (Was it not you, Sir, who said it was difficult to establish whether the Mini or the Imp cornered better without consecutive tests wearing “go-faster gloves”?)
Petrol; 38 m.p.g., overall with main road/motorway cruising 70-75 m.p.h., and generally full use of gears when accelerating.
Oil; 600 m.p.p. at 10,000 miles and falling steadily.
Water; Nil. No sign of early coolant troubles.
Tyres; 50% worn at 10,000 miles. Even wear obtained by move rounds at 2-3,000-mile intervals.
In conclusion, I was never more reluctant to sell a car and would have liked to have kept it for No.2—often No.2. I should like to know whether other readers can put forward reasons for the apparently slow growth of enthusiasm for the Imp. I may be prejudiced but I know of many Mini owners who were less pleased with their first 10,000 miles.
Liverpool. A. Colman.
I have been interested by the correspondence relating to the Hillman Imp in your November issue. It was with certain reservations that I took delivery of a Singer Chamois in replacement of my 1964 1 1/2-litre car, in May. (I wished for more sound insulation and the SP41 tyres of the Chamois.)
After 5„000 miles, one water pump and a trans-axle oil seal (500-mile service), I am highly satisfied with this car. Apart from the two points just mentioned and a heater blower which was not connected on delivery, there have been no teething troubles whatever. The little engine is completely untemperamental, has never missed a beat, and seems smooth and extremely lively. Starting is instantaneous. A little oil was used during the first 3,000 miles but this has now decreased to an almost negligible amount, as mentioned in the handbook. Petrol consumption to 4,600 niiles averaged 45.6—I am light-footed but not a dawdler!
The car can show a clean pair of heels to just about anything of its capacity unmodified, and to a good deal of even heavier machinery. I have seen an indicated 90 m.p.h. on the speedometer on M1 (the wind must have been following us) and at this speed the car felt quite stable and the engine like a turbine. My more normal cruising speed is from 60-65 m.p.h. when the car feels to be completely unstressed and there is a high standard of quietness for such a small car. Oddly enough there is no wind noise.
Handling and stability are very good indeed and the car can be cornered with great confidence—I have never experienced any suggestion of tail heaviness and were it not for the sound of the engine from the rear it would be difficult to realise it was rear-engined. I think the SP41s help here.
General design appears to have had careful thought. I am 6 ft. 2 in. but have no difficulty in fitting in comfortably with the seat well back. The accelerator position can be rather tiring on long journeys, although I understand this has now been modified. Instruments and controls are exactly where required and the gearchange is a delight.
The brakes on my particular car are adequate but less smooth under hard application than I like. I have a feeling one of the rear drums is not quite true, though I have so far been unable to convince my dealer or this.
After 29 years’ driving I can say that this is truly one of the cars I have enjoyed driving most and it could never be regarded as dull. Never a drop of water has found its way inside—even during our last summer!
I feel bound to comment on the letter from a correspondent in your November issue. I have sat in an Imp far too long to let his lack of understanding as to why so many people have criticised this car continue any further.
My Imp was purchased in December 1963. The early faults were small. Namely, the sun visor worked itself free very rapidly, several chromium parts had to be replaced after inspection by Rootes, rust formed within weeks on various parts of the body, and leaks developed round the bonnet hinges. Fuel consumption, never above 34 m.p.g., fell to 24 m.p.g. over several thousand miles. The pneumatic throttle had to be replaced. At 1,400 miles the clutch failed. At 18,200 miles the water pump packed up. One would have thought that the replacement parts would have lasted longer, but the clutch again failed at 26,500 miles, and the water pump at 24,700 miles. The latter involved me in delay for a day and a hotel bill, in which Rootes were not interested.
Both king-pins were replaced within the first year of use, as were the silencer (fractured rear bracket) and automatic choke. After indifferent performance which my then garage seemed unable to cure, the carburetter was replaced.
My next purchase will not be a Rootes product. This is unfortunate since I have many pleasant memories of the 1930 16/20 Humber tourer I formerly owned.
Cuddington. L.G. Machin.
Your un-named correspondent last month criticises those who run down the Hillman Imp and, never having owned one himself, goes on to praise it to the skies. May I, as an owner, be permitted to redress the balance with an account of my own experiences which, from inquiries among friends and acquaintances who also possess this model, I gather to be far from unique. I purchased the car in April 1965 and it has been a continual source of trouble ever since. Your correspondent blandly asserts that the early trouble with the automatic choke has now been sorted out; nothing could be further from the truth. Despite repeated adjustments it has never functioned properly. This, however, is a small matter compared with that which followed. In early September; with the car barely five months old, I suffered a complete mechanical breakdown; the cause of the trouble—a common one in this model, I have since learned—was traced to the gearbox. As if this in itself were not bad enough, I was told that spare parts took upwards of a month to deliver and that I should reckon on being without my car for several months. It was only by dint of almost daily ‘phone calls to Rootes’ Head Office that I eventually got it back in just four weeks.
My troubles were not yet at an end, however. A week ago I again had a complete breakdown, the trouble this time being with the clutch.
I consider this car to be an absolute disgrace and its bad reputation, which your correspondent finds so hard to understand, fully justified. However, if he is still an enthusiast, perhaps he would care to have my Imp ? I can assure him that no reasonable offer will be refused.
Guildford. M.G. BROWN.
I, in common with one million others, own a B.M.C. Mini. For the price of £470 I think it is an exceptionally good car. The reliability has been proved over 21,000 miles since February 1965. There are, however, two lamentable exceptions : the suspension, which in my opinion has made fast cornering unnerving for passengers (it also collapsed on both sides two weeks after delivery), and the water pump, which gave up the fight at 17,000 miles. My eager neighbours call round to see when the gearbox is going to break up, the doors fall off, or the engine lock up solid, but so far in vain. My own car is very noisy inside; the 650-c.c. Triumph Bonneville motorcycle that I used to own did not tire me so much.
I have managed to improve the top speed and acceleration to Imp/Hornet standards by fitting a Derrington exhaust/inlet manifold, and one stage richer needle for the carburetter. The car is at present running on Dunlop SP41 tyres, which I find very durable and predictable.
Warnham. J.D. Walton
In defence of the o.h.c.
I wonder if you would care to publish some facts and figures on mass produced engine manufacture, in reply to Mr. Hindmarsh last month ? It is certainly true that an o.h.c. layout is more expensive than push-rods if we compare a Vauxhall Viva with a Hillman Imp-type arrangement (I choose the Viva since it’s probably the least expensive, to manufacture, whilst being very sound engineering). The increase in cost comes from having to make removable bearing caps for the camshaft, cast and machine an extra piece (the tappet block), use larger tappets with adjusting shims, a longer timing case with chain tensioner and a chain about twice the normal length. This more than offsets not having push-rods, rockers and pedestals; in addition, another source of oil pump and distributor drive has to be provided. If, however, we make the comparison with the Opel Rekord type of o.h.c., there probably isn’t much difference since the cost of separate skew gear for the oil pump and distributor, larger pressed steel timing case and belt tensioners is offset by cheap sintered pulleys and belt, no tappets or tappet bores and no push-rods. The rocker arrangement stays the same and provides as easy a method of servicing as the o.h.v, layout. The provides inertia of the rocker is in fact less than a bucket tappet and the system is probably the best and the cheapest. By way of comparison, the total reciprocating valve train weight of such a layout is at least 10% less than using a bucket tappet and about half that of a push-rod system.
The advantages of weight reduction are that either the spring load can be reduced to give much less wear, or the cam acceleration rates can be increased to give better power and torque whilst retaining tractability. The present power outputs of small car engines are very dependent on the latter and partly for that reason the industry is changing to o.h.c. since the wear rate with push-rods would be unacceptable. If anyone doubts that wear occurs in modern valve gear, let him strip out the cam, tappets and rocker shaft after 100 hours running from new; they will probably be thrown away in disgust and new parts fitted. Power unit assembly is certainly not a major cost, accounting for only about 1% of the total and is about the same cost as doubling the length of the timing chain. If expertly organised with sensible operators, results not much inferior to Rolls-Royce or racing mechanic practice can be achieved. The superiority of the latter lies in prior modification of the components rather than putting them together, which is skilled but simple fitting. For example, one manufacturer, at least, finds it considerably cheaper and quicker to feed special rally engine and gearbox components down the normal assembly line in about 25 minutes rather than spend days doing it individually by hand. And provided all the power tools are in correct adjustment the result is virtually identical. With any luck they will accidentally, lose one into a production car one day, which should make running in quite exciting. I can just imagine it “I’m sorry madam but I can’t make it tick over under 1,700 r.p.m. You’ll have to put in a guarantee claim !”
Coventry. C.B. Mynott
The Ford Corsair V4 road test.
As a reader who has returned to Motor Sport after a few years absence, I was interested to read your comparison of the Ford Corsair V4 1700 model and the Cortina GT. I bought one of the new V4 models immediately it was announced—incidentally I am still waiting to see another on the road.
The Ford replaced the second of two Riley 1.5s, which gave reliable, if not entirely comfortable, service for 85,000 miles between them. The later model (1963) did suffer from a host of minor rattles and ailments, including, in the first few months, the replacement of the battery and fuel pump. It also had a ravenous appetite for tyres, making even SP41s crack round the sidewalls.
The Ford was therefore purchased as a change from B.M.C. products. Most of your criticisms of the Ford are very fair, however one or two points spring to mind. On my car the clutch is so light that it takes some getting used to. Also your reported petrol consumption seems rather high. Although I have not made a careful check, my car seems to use no more petrol than the Riley, which, carefully checked, returned 30-32 m.p.g.
The steering of the V4 developed an ominous rattle after 1,500 miles. The official dealer reaction was that this was a “common Corsair fault” and they would put it right. This, plus the search for another steering rattle, a hunt for a gremlin in the back seat and an unsuccessful investigation into the appearance of the generator warning light at normal motoring speeds, means that my car has already been off the road for four days of its young life.
Incidentally, this provided me with the experience of driving an ordinary Cortina 1200, generously lent by the Ford main dealer. This car certainly had a much heavier clutch and less positive steering than the Corsair.
I now hope to experience some of the reputed Ford reliability, although there are still the products of three more of the “Big Five” to try.
Lowdham. J. Bryan Dixon
John Cobb’s Napier Engines
I have read with considerable interest your article on John Cobb’s land speed record attempts, noting the emphasis you place on certain facts quoted in italics. As a further tribute to the efforts of those engaged, I would seek to put on record that Napiers were approached to afford test bed facilities to enable engine tuning and power checks to be made. These unfortunately could not be carried out due to the fact that suitable beds were non-existent. The marine version of these engines, the unsupercharged and less powerful “Sea-Lion,” required an inclined bed to simulate the attitude of the engine in the boat to suit its power line angle and these beds were fully engaged to meet an impending war. For this latter reason alone the manufacture of a new bed was out of the question. The point I am making is that these supercharged engines were presumably tuned in the chassis for the 1939 record attempt, and apparently very successfully—a truly formidable task.
A further point of interest is that these engines were groundboosted for air record purposes, whereas Bonneville Flats are at approximately 3,000 ft. altitude and a certain power loss therefore resulted. Under the aegis of A.J. Penn, the interesting task befell the writer to help in calculating the optimum supercharger gear ratio for maximum power at the record run altitude. This resulted on paper in a gam of 130 h.p. New gears were made and we had the gratification of later experiencing Cobb’s creation of a new record. Alas! his glory was diminished by the almost immediate outbreak of war. For this quiet, modest and unassuming man of notable purpose and achievement, his end was indeed tragic.
To misquote Wordsworth (with apologies to Milton) :—
“Cobb ! thou should’st be living at this hour.
England hath need of thee,
She is a fen of stagnant water, etc., etc.”
Weybridge. I.I. Ellis.
That Chevrolet Parcels-Shelf
Chevelle Malibu :— You state in the November issue in respect of the Chevrolet, “I am astonished, knowing the store G.M. set on research, that the shelf behind the rear seat is unlipped, so that anything stored thereon soon falls off, encouraged by those ‘sudden’ brakes.”
This leads me to comment that when I visited the United States a year or so back, it was pointed out to me that this was deliberate, and that parking things on the shelf behind the rear seats was discouraged, for two reasons: (i) visibility, and (ii) in a shunt, objects on the shelf could hit and injure any of the occupants of the vehicle. This seems fair enough, I think.
Brooklands. Glyn Lancaster Jones.
Mercedes-Benz 600 Speedometer accuracy
I think it should be emphasised, in relation to your interesting article on the Mercedes 600, that one has only reached slightly over 90 m.p.h. (92 actual) when the speedometer is showing 100. Why do manufacturers try to deceive their customers by fitting fast speedometers? Cannot you, Sir, as the most fearless Editor, compile a list of those who do this as a matter of policy. It would, I assure you, be a public service, and in keeping with your paper’s fine reputation.
Edenbridge. Hugh Hunter.
[Time permitting . . .! We do, when possible, quote speedometer against actual speeds in road-test reports. It certainly seems that Mercedes-Benz, Alfa Romeo, Simca and Renault are the worst offenders, whereas B.M.C. contrive accurate readings on the Austin Westminster and 1800, Rootes on the Singer Vogue and Chamois and Ford on the Mustang. Skoda even have a slow speedometer.—ED.]
Betting on Motor Racing
There has been a lot of talk recently about advertising on racing cars, as a way of providing increased revenue. This can be acceptable to very few people I feel; however one further way has struck my mind that I should imagine would be more easily acceptable and just as profitable; why not have a sort of Motor Racing Tote, run by the R.A.C. or one of the clubs and accept betting in the same way as the Horse Betting Levy Board do. Revenue could then be distributed to needy causes and this would also possibly increase public interest in the Sport.
Smallthorne. W.H. Mawby
[Well, we don’t want to encourage gambling at motor races, but it is a fact that the Right Crowd at Brooklands had a Tote in 1928/29 (in a converted omnibus) and there was an attempt at Aintree to start motor-racing Pools, which failed.—ED.]
S. Hall’s letter in the November issue, drawing attention to the fatuous prices charged for brake linings, prompts me to offer a simple explanation.
Accessory and component manufacturers base their charges entirely on what the buying public will stand—the genuine value of their offerings having no bearing on the subject.
I was recently forced to pay over £1 for a complete rear door lock mechanism in order to rob the operating cam; buying the cam by itself was apparently quite out of the question. I was, therefore, effectively paying over £8 per lb. for die-cast metal !
True value for money is a thing of the past, and if Vance Packard’s “The Wastemakers” is anything to go by, the future looks even less rosy.
Lee-on-Solent. P.R. Walwyn, Lt. Cdr. R.N
In reply to I.R. Marvin’s letter in the November issue, might I point out that the reason why little was said of the Hillman Imp is that foreign car manufacturers beat us “hands down” in their propaganda, Press reviews and salesmanship. This must reflect on the market and correspondence. I can give a recent example of this state of affairs.
I sent away for brochures on the Fiat 850 and the Hillman Imp, very competitive as there is but £4 difference in price out here. Within two days the Fiat agent had come to see me with the leaflets, brochures etc., and an admirable sales talk. He gave me a complete description of the car, its capabilities and quoted me extracts from leading British magazines to support his story. Every conceivable angle concerned in owning such a car was approached to the last detail.
Two days later the Hillman (Rootes Group) agent called at our barracks. If the Fiat agent could go to the trouble of tracing me to my workbench it was a little alarming when I learnt that I had to go and see the Hillman agent. (No drive ?). And my trouble wasn’t worth the time; he had no brochures or literature with him, he couldn’t give me any details as he couldn’t remember the whole Rootes Group products he was agent for, he gave rough and ready particulars of payment and generally gave the impression that he couldn’t care less whether I bought one or not.
If this is the tone of our “Export Drive” what state must our home market be in ?
B.A.O.R. J. Thomas
The Puncture-Proof R.A.C.
I thought your readers might be interested in my recent experiences in London of the lack of hospitality to a visiting motorist both by local garages and by the R.A.C.
Finding a flat tyre after my first night’s stay, I contacted seven garages in all in an unsuccessful effort to get service. Then I contacted the R.A.C. (Whitehall 4343) of which I have been an associate for 12 years, and asked for their help. On learning that the car weighed more than 30 cwt. I was informed that no help could be given. I remonstrated with the speaker who then contacted the manager who confirmed this fact. Eventually, after a good deal of persuasion, a local garage changed the wheel but would not repair the puncture. I left London and had the tyre repaired immediately on arrival in Hastings. One of the main reasons for joining the R.A.C. is to use their emergency service when necessary. Needless to say, I shall not renew my subscription.
I thought too that the relevant tourist board should know these facts. What must foreigners think ?
Glamorgan. F.W. Landgrebe
Citroen Safari Experiences
I have just completed a year with my 19th car, and first Citroen (Safari 1964; DW specification), and I feel that your columns are the best place to air my strong and contradictory emotions.
In the first place, I am hopelessly hooked; like most other Citroen owners I have spoken to, I doubt if any other car could satisfy me again. But oh, how many, many things could be better.
To get my grumbles off my chest, in no particular order.
(1) Why have power steering if it doesn’t help you to park ? The Citroen is heavier at parking speeds than my previous 3.4 (unassisted) Jaguar on Cinturatos !
(2) Why be proud and make your own heater, when good standard ones exist ? The Citroen and the Jaguar both have feeble heaters of a rudimentary kind compared with the quick, hot, thermostatically-controlled job on, for example, the Vauxhall Victor.
(3) Having built a sensationally good suspension system (see below), why in heaven’s name can’t they, of all people, take the little bumps out of the Michelin Xs? I have done a number of runs in the Peugeot 404 and Lancia Flavia coupe recently, and while neither approaches the Citroen in overall suspension, both, on conventional steel springs and Xs, ride the cat’s eyes perfectly softly.
(4) The drive shafts; it’s taken ten years for these awful things to be changed (just too late for me ). Mine are particularly dreadful. shaking the whole car at 25 m.p.h. on acceleration or braking. Slough, and the agent, say this is absolutely normal, but it doesn’t happen on an identical car belonging to a friend.
(5) My gripe about the engine wasn’t really about the lack of power—you’re always going faster than you think—but about the row it makes; and to judge from a road test of the DS21 in a French paper (generally pro-Citroen) it appears that more power has been achieved at the expense of even more noise and vibration. Why don’t they buy the Corvair engine under licence ? Again the Peugeot proves that you can be sensationally smooth on four cylinders.
(6) The wipers. They would disgrace a van, with their noise, wobbles, one inadequate speed and tiny wiping area.
But it remains infuriatingly true that I arrive safer, fresher and sooner than I did in the 3.4 than when I’m hurrying in the Peugeot and look at the dial it usually shows about 75; in the Citroen it’s about 90. [It had better not, until after Easter !—Ed.] That it gives me from 22-28 m.p.g. It looks as if it will never wear out (body rust apart—all cars rust these days !) and that I’ll probably continue this love-hate relationship for life.
But how I wish someone with a faint idea of what refinement means would join with Citroen to produce the truly perfect car.
London, S.W.19. Tom Jago.
The R.R.L. as road users
In your Editorial for November, 1965, you described an incident in which you had been involved and concluded . . . “(2) That if someone so excitable and aggressive drives cars for the R.R.L., his findings lack the authority one has a right to expect from cool, dispassionate scientists employed by a government organisation!”.
You had previously given an account of this incident on the telephone to the Laboratory and had been told that no-one had the right to use the Road Research Laboratory’s name in the way you described. Following your telephone call an investigation was made, as a result of which it has emerged clearly that no member of my scientific staff was involved in any such incident as was described in your Editorial. The only vehicle which appears to answer the description given to the Laboratory by yourself is one belonging to a labourer on the Laboratory staff who, at the time of the incident, was absent from the Laboratory and who is now in hospital [nothing to do with me !—Ed.] and we have not yet been able to obtain from him his account of what happened.
In these circumstances, and as we have not been able to obtain his version of the occurrence, I do not propose to comment on the circumstances but I am writing to make it clear not only that the Laboratory would disapprove of any member of its staff behaving in the way described but that no one on my scientific staff was involved in the incident.
West Drayton. D.J. Lyons. Director of Road Research. Road Research Laboratory.
Alfa Romeo Advertising
I really think that Alfa Romeo are becoming a little over enthusiastic with their advertisements. The one in front of me reads “Here’s the Alfa Giulia Super— the fastest 1,660-c.c, production saloon in the world. Its top speed is over 110 m.p.h.” It then goes to say “Alternatively, if you’re satisfied with a mere 105 m.p.h., there’s the Giulia Ti for £1,397 3s. 9d. (the second fastest 1,600-c.c. saloon in the world).”
On reading this the Lotus-Cortina immediately came to mind, because if it is not faster than the Super it is certainly faster than the Ti and for a considerably smaller capital outlay. Isn’t it about time these “nonsense” adverts were stopped ?
Worcester. N.C. Garland. [All of which is of little moment now, unless we get rid of Mr. Fraser.—Ed.
An Excellent Suggestion
It sometimes happens that one would like some means of warning one’s fellow road-users of a potential danger, such as a flood, herd of cattle or sheep, an accident, a patch of ice, etc., or of the presence of a speed-trap. How to do so is the problem. Making an improvised signal and planting it beside the road is impracticable and possibly illegal. Lamp flashing isn’t always understood.
May I suggest that after passing the hazard a driver should put on dipped headlamps and leave them on for a few miles ? This would enable observant on-coming drivers and riders to be prepared, and enable them to reduce speed in good time. Dazzle could hardly result from dipped headlamps in daylight nor are they, so far as I know, illegal. Only a daylight warning, I admit, but it could save fellow motorists damage and expense.
London, EC.1. “Safety First”.
[This seems an excellent suggestion, which we of Motor Sport propose to adopt at once. If other drivers flash at your dipped lamps put it down to ignorance or the fact that they don’t read this journal ! You will be able to go “softly-catchee-monkey,” slowing down and looking about you !—Ed.]
The Maybach Mystery
I was very interested in your article. “The Maybach Mystery,” for I machined the coupling flange for the Mercedes’ flywheel. I was machine shop foreman at the Canterbury Motor Co. (now Rootes). When the crankshaft came to us it still had the propeller boss on it, which we could not move under hydraulic pressure, so I had to machine it off; it was not keyed. Integral with the boss was a gear wheel.
I started with a billet of chrome vanadium steel weighing about 40 lb. The taper bore was, I think, about 6 in., the coupling had to fit exactly the same position as the prop, boss for the correct alignment of the gear wheel, which I cut on a vertical stoner.
Canterbury. C. Greensted.
I agree that Mr. FitzPatrick’s suggestion that the Isotta Maybach may have been powered by an interim 5-valve BY type engine sounds more plausible than the conversion from 4 to 5-valve layout reported by the Motor in 1922. However, the other peculiarity referred to in the original Motor report, i.e., the provision of a cut-out to prevent damage due to oil pressure failure or over-revving, was not bad reporting as you postulate.
Among the early aero engines in the Science Museum, South Kensington, is a Maybach engine dated 1915 and corresponding to your description of the AZ type (four engine mounting points and timing gears at the front). According to the descriptive note, “an electric tell-tale device fitted on the end of the magneto drive operated whenever the oil pressure became dangerously low or the engine exceeded a set r.p.m.” This can clearly be seen on the display engine, although whether it operated as-a cut-out or merely as a tell-tale is not clear as most of the wiring has been removed.
As to the air blast circulating through the crankcase, the only external signs are two large (1-in. bore) unions fitted where one would normally expect drain plugs in the sump. These appear more like water connections, perhaps for an internal heat exchanger, than part of an air blast system a la Bugatti.
If these ingenious devices are lacking from the engine of the Metallurgique this may be because it was all earlier engine (No.30) in the AZ series than the Science Museum’s example (No. 89). If so, it seems likely that these developments would have been carried through into the suggested BY 5-valve series engines, and that the only error involved in the 1922 Motor report was the reference to these features as modifications introduced for Brooklands use by Eldridge rather than standard features of the later engines.
Incidentally, the aero engines on show in the Science Museum are well worth a visit for any vintage car enthusiast.
Great Chesterford. M.L. Clark