THE NEW TWIN-CAM M.G. -- from MOTOR SPORT magazine, August 1958 -- Thanks to John Lambie for the scan of this article.
It has been known for some time in motoring's inner circle that the Nuffield organization has been working an a twin o.h.c. version of the existing M.G.-A. to be supplementary to that popular 1-1/2-litre sports car. Indeed, the new sports car was expected to appear at the London Motor Show last October but snags arose, delaying its announcement until the middle of last month.
The new car is virtually the same as the push-rod o.h.v. model-A, except for the new engine and disc brakes all around. The twin-cam engine has a capacity or 1,598c.c. and gives 108 b.h.p. at 6,700 r.p.m., the output being 97 b.h.p. at 5,500 r.p.m. The engine capacity has been increased to take full advantage of the International Touring Car classification. As a speed of 120 m.p.h. is claimed for the twin-cam M.G. the makers have wisely specified disc brakes. These are Dunlop, in conjunction with ventilated centre-lock disc wheels. The body lines are unaltered, but the words " twin-cam " on boot lid and scuttle air exits give the game away to those surprised by the new M.G.'s performance.
Various extras are available for the new car, but its basic price, L1,265 17s, inclusive of p.t. ( a coupe costs L1,357 7s), is extremely competitive for a 120 m.p.h. car.
The engine is basically a 4-cylinder B-series B.M.C. unit with enlarged bore and a light alloy head with valves inclined at 80* and actuated by twin o.h. camshafts. The camshafts are driven by Duplex roller chain from a half-speed shaft located where the camshaft is on the normal engine, this shaft being driven by a gear-train from the crankshaft. The crankshaft has been stiffened, and different con-rods and pistons are used. The compression ratio is 9.9:1. Polished alloy cambox covers make a handsome engine, to accommodate which the coolant header tank is situated beside the near side cambox. Incidentally, the makers indicate that the M.G.-A. cannot be converted to twin-cam specifications, nor will disc brakes be available for this model.
The new engine has been in process of development for considerable time. Prototype M.G.-A.s appeared at Le Mans in 1955, two of them finishing, in 12th and 17th places. For the T.T. that year one of the M.G.s had a twin-cam engine and two had Girling disc brakes. The twin-cam car was said to give nearly 110 b.h.p.; it retired. In 1956 the M.G. E.X.179 used a twin-cam engine when it successfully broke International Class F records at Utah and last year E.X.181, which Phil Hill and Sterling Moss drove so fast at Utah, had a supercharged 290 b.h.p. twin-cam engine. So it was inevitable that this classic valve gear would sooner or later figure on production M.G.s.
The longer you wait the greater the anticipation, so it was with interest that we drove to Chertsey on July 14th to try the new twin-cam M.G. over a course at the F.V.R.D.E., which the Nuffield organization had borrowed for the day.
Four open twin-cam M.G.s were available, although one retired early with a broken dynamo bracket and later another was crashed. (We are yet to identify the fourth car, and we are yet to identify which one crashed, as it was driven by a drunk BMC band member. We also know the number plate PMO946 is in the photos on the day but it's a light coloured car in the photos but in reality is a Red "Demo" production car, so clearly a number plate switch, perhaps the dynamo bracket issue).
The makers claim that the best change-up speed is 6500 r.p.m. and that the car goes on accelerating beyond 100 m.p.h., this speed being reached from rest in 31 sec. and 110 m.p.h. in 38 sec. Maximum speed is claimed to be approximately 120 m.p.h. (But see below 1).
The F.V.R.D.E. banked track was an unfortunate place at which to stage a demonstration of such a car, because even the better drivers could scarcely reach 100 m.p.h. at the end of the short straight. The new engine seemed reluctant to go beyond 6,000 r.p.m. and after six miles " ran on " furiously when switched off. The handling was excellent round the rough bankings and through the reverse curve but the steering was heavy and less pleasant than that of the M.G.-A. It was necessary to drive most of the lap in third gear to obtain a reasonable speed and the revs, appeared to rise reluctantly, compared with the push-rod engine. One journalist was clocked to lap in 1 min. 28 sec. and anything under 1 min. 31 sec. was good going on this approx. 2-mile track. Lowering the front tire pressures made the car much more stable. The engine gives plenty of power, without being noisy. A careful check of the oil-level every three laps was kept by the M.G. mechanics and the engines were seen to be running on a rich mixture.
Not a great deal can be determined by such a track test. We had hoped to publish a full road-test report on the new M.G. in this issue of MOTOR SPORT. However, at Chertsey we were informed that no car was available for this purpose as the hoped for performance is not being realised. Consequently, we must reserve judgment on what could be a quite outstanding sports car, particularly bearing in mind its price. Taking the average of two independent rest reports which have been published, the twin-cam M.G. at present does 114-1/2 m.p.h. and reaches 100 m.p.h. in 40.7 sec., with a fuel consumption of 22 m.p.g.
---W.B. - [Bill Boddy]
(N.B.---The performance figures for the current twin-cam M.G. is of academic interest only in this country, because the first seven months' scheduled production is accounted for by orders from America and Canada, which are worth over a million dollars.)