Jack Brabham Viva GT

HA Brabham

Obviously this is a very healthy background, with development engineers having the necessary knowledge and experience to bring the chassis into line with their engine tuning accomplishments. Thus, although the various modifications incorporated in the Viva GT can be applied piecemeal (on the instalment system, so to speak), it is much more satisfactory to have the car as an entity, the all-in extra cost being £139. Over and above this, the car tested had the special four-branch exhaust, road wheels with wide-base rims, a 15in. wood-rim steering wheel and Interior Silent Travel, adding a further £44 5s. Briefly, the conversion package comprises a specially tuned engine with twin Stromberg carburettors, lowered suspension front and rear plus an anti-roll bar at the front and Koni dampers aft, and a replacement instrument panel.

In standard form the 1,057 c.c. 4-cylinder engine develops 44 b.h.p. net at 5,200 r.p.m., and to bring this up to 60 at 5,800 the cylinder head is considerably reworked, with enlarged and polished ports, modified combustion chambers, larger inlet valves and special exhaust ones, all with double valve springs. The compression ratio is raised to 10.0 to 1 from 8.5, and a fabricated steel inlet manifold carries two Stromberg CD125 (1.25in.) constant vacuum carburettors with small pancake air filters. A straight-through exhaust silencer and new tailpipe are included. For anyone intending to race the car quite a bit more can be done to warm the engine further.

Front suspension of the standard Viva has double wishbones and a transverse leaf spring in tension, and to drop this end the leaf ends are bolted to extensions welded to the undersides of the lower wishbones. Stiffer front dampers are available for competition use. At the back the Viva has a live axle with half-elliptic springs, and that the axle is located by a short torque tube enclosing the rear section of a two-piece propeller shaft; also that it is linked—rather than bolted firmly to the springs. In this conversion the springs are reset flatter, a less resilient rubber mounting supports the nose of the torque tube, and Koni adjustable telescopic dampers replace the Vauxhall ones.

HA Brabham

While all these changes make the Viva more suitable for rallying, the main attraction lies in its extra qualities as a road car for everyday use. Thus, while the improvement in performance is enormously worthwhile, the tuning has Viva’s factory options, there is plenty of braking power and capacity to counter the increased acceleration and higher top speed; but stiffer location of the torque tube seems to have eliminated a tendency to rear-axle tantrums during hard braking.

Right from the start the Viva has been noted for exceptionally light controls-steering, gear lever movements, clutch and brake. Current models have a slightly ” quicker ” steering gear ratio than the early ones, yet even with the neat little 15in. wood-rim wheel fitted in the test car-reducing one’s mechanical advantage a bit more-the mechanism is still delightfully light and, of course, more responsive.

One takes for granted that a ” converted ” car will go that much more rapidly, and the real surprise in this one is the change in its road behaviour. Whereas the standard one is very satisfactory for its purposes, this GT lives up to its pretensions. Sitting closer to the road on its lowered and stiffened suspension, and with wider rims to spread the tyre profile, it has acquired excellent cornering power for an orthodox chassis, together with the ability to hold its line accurately through fast, open bends without drama. There is little body roll, and the back axle (with noisy final drive gears in this example) plays no tricks However hard one drives, the physical effort involved in correction, the pressure of a finger on the lever and little more than the weight of one’s foot on the clutch pedal for a gear change, and scarcely more than this on the brake for an emergency stop. There seems to be a time saving in responses where the human muscles are exerted less, and of course the physical drain is the much slower when one has to drive hard for a sustained period.

In the engine department the object has been to add as much power as could be managed without losing mechanical refinement, quietness or low-speed tractability, so that the car remains at least as practical and pleasant for everyday use as the standard product. There must be plenty in hand for further extension, since in this form it still feels exceptionally smooth and sweet, so should hold its tune well. The exhaust note is quite restrained, without any give-away sporting barks or burps to draw attention to the car. The recommended rev limit is 6,500 r.p.m. but the practical maximum is nearer 6,000, and the top speeds shown in the data for the indirects are equivalent to this figure. Although the standard car can also reach these, it naturally falls far short of the Brabham car in top, the improvement in mean maximum speed being 10 m.p.h.-from 77 to 87.

However, since the GT engine’s power peaks at 5,800 r.p.m., the lower gears are useful right to the rev limit, and hence the standing-start acceleration figures are very substantially better. Thus the GT can reach 70 in less time than the normal car takes to 60. The top gear acceleration figures are also revealing; without having lost anything in low-speed getaway, the GT cuts 5.8sec off the 40-60 m.p.h. range, for instance.

HA Brabham

While these figures are excellent, if not remarkable, the car’s charm lies in its abilities and behaviour as a whole.

Autocar 14th may 1965

Autocar 14th may 1965