Otto Cilindri: Moto Guzzi V8 Grand Prix Racer

Fast, fragile, flawed and fantastic, the Moto Guzzi V8 of the 1950s should have ruled Grand Prix racing. But it didn’t…

Otto Cilindri: Moto Guzzi V8 Grand Prix Racer

Otto Cilindri: Moto Guzzi V8 Grand Prix Racer

The Guzzi V8! If you dabble the least bit in motorcycling history, you have heard of this complex and ambitious machine, built in 1955 to dominate 500cc Grand Prix racing.

At its best, the V8 had the numbers to do it. In 1957, when Gilera and MV were making no more than 67-70 horsepower from their inline-Fours, the V8 could summon 80 crankshaft hp at just over 12,000 rpm—a power level not reached again in GP racing for 10 years. It had staying power, being liquid-cooled at a time when every competitor was air-cooled. It was extremely fast—timed at 178 mph at the 1957 Belgian GP.

Yet it never won a single Grand Prix. Although fast on certain courses, it DNFed often. The V8 was a classic case of an ambitious program whose development needs exceeded the resources of its creators. The list of such failures is long—think of BRM’s V16 Grand Prix car engine of the 1950s, Honda’s oval-piston NR500 of the ’80s, Chrysler’s IV-2220 inverted V16 aircraft engine of 1944. The engineering problem is to advance the state of the art by enough to win but by no more than can be made ready for use in the time available.

An astonishing five months elapsed from the moment when Guzzi principal Giorgio Parodi gave the project his approval until the first engine ran. Thirty days later came the first track test. Lead engineer Giulio Cesare Carcano, assisted by Umberto Todero and Enrico Cantoni, followed a logical path to a V8. Guzzi had nothing competitive in the 500cc class. Its “bicilindrica,” the 120-degree V-Twin that had won the TT in 1935, had been retired as too slow in 1951. Its replacement, a liquid-cooled longitudinal four-cylinder, had been troublesome and ill-handling, winning only one GP. It was retired in 1954, leaving Guzzi with what it did so well: light, agile Singles with broad pulling power. With such Singles, Guzzi won 350cc world championships 1953-57 inclusive, defeating DKW’s 10,000-rpm two-stroke Triple and Gilera’s transverse inline-Four.

Moto Guzzi V8 Grand Prix Racer front profile

But Gilera and MV were entrenched in the 500cc class, with highly developed Fours whose handling had benefited from the knowledge of transplanted English riders like Geoff Duke and John Surtees. These intelligent rider/engineers carried with them understanding of what had made Norton’s venerable Single so good in 1950-52—a strong chassis, forward engine position and supple hydraulic-damped swingarm and telescopic front suspension.

Guzzi’s 500cc Single might win an occasional GP (as Bill Lomas did at the Ulster TT in 1955) but never a championship. Carcano knew that Singles and Twins were finished in 500. Horsepower is basically cylinder-filling ability multiplied times rpm, so if Guzzi built another four-cylinder, it would confront all the development already completed by Gilera and MV. To make up for the opposition’s experience in filling the cylinders of its Fours, any Guzzi challenger would have to be capable of higher rpm. That, in turn, would require a greater number of smaller, higher-revving cylinders.

Six? A Six would be wide, and European tracks—still based upon public roads in many cases—emphasized top speed and aerodynamics. Increased width was unacceptable. Then a V8? Only water could cool the rear cylinder bank, but sketches and estimates soon showed that such a V8’s crankshaft would be less than 13½ inches wide. Even adding two inches for the dry clutch and 2½ inches for a water pump, the resulting package slid into a fairing an inch narrower than a modern Ducati V-Twin’s. Who could resist?

Don’t think of Guzzi as a quaint little European manufacturer quietly crafting oddities in a backwater. At the time, Guzzi had 800 machine tools on its production floor and was a major transportation producer. On staff were craftsmen in every specialty. The company had produced aircraft parts in the war and understood how to quickly push projects from paper to metal.

The V8 engine is a beautiful object, and its details reveal Carcano’s devotion to weight control. The magnesium unit crankcase is open on right and left, allowing the crank to be slid in sideways. The middle three of its five main bearings were then bolted up against main webs at the apex of the Vee.

There are no separate cylinder blocks. A portion of the cylinder water jacket was formed as part of the crankcase, and the rest was cast as part of the cylinder heads. The outer main bearings were carried in right and left engine covers, which also supported the vertically stacked gearbox. Wall thickness of crankcase and covers was 4mm—under 3/16 of an inch—foundry work of a high order.

Moto Guzzi V8 Grand Prix Racer sketch

Moto Guzzi V8 Grand Prix Racer sketch

To eliminate the stresses and extra mass of bolts required to make a head gasket work, the iron cylinder liners were screwed into the two heads. Each head with its downward-projecting cylinders was then slid into place. Only two or three years earlier, Aurelio Lampredi had pioneered this technique at Ferrari, and today it is again used in Formula1.

This was a two-valve engine with a very modern, narrow, 58 degrees between the intake and exhaust stems. The result was a flatter, faster-burning combustion chamber than the 90-100-degree chambers of rivals Gilera and MV. Why buck the trend? Guzzi had found a power advantage in the narrow valve angle in its Singles. The V8’s four cams were driven by narrow, delicate spur gears in a case on the engine’s right side. All valves seated directly on the aluminum alloy head material, no seat inserts. Bore and stroke were 44.0 x 41.0mm, the very dimensions Honda would in five years choose for its four-cylinder 250s.

The agony began with the machine’s first appearance, at the 1955 Belgian GP, where the studs securing the crankshaft main bearings broke. Look at these engines from below and you will see nine plugged holes that allowed access to these fasteners. In the fall of 1955, it was decided that replacing the original 180-degree crank with a 90-degree would cut stress on main-bearing webs, and two variants were evaluated. The first cranks were one-piece forgings, with con rods, inner main bearings and roller cages split for assembly over it. Although this seems makeshift, it had been a successful method of construction before WWII, used even by Mercedes for its mighty 600-hp supercharged GP cars.

The V8’s “shakedown year” was planned as 1956, but the shaking never stopped. The tally was water-pump failure, broken big-end cages (while leading at Hockenheim), unscrewed tappets, a collision, a stoppage, overheating while second to Geoff Duke’s Gilera, then a crash in a national race and a big-end failure at the Monza GP des Nations. Not one finish. Meanwhile, Guzzi’s super-light 350 Singles dominated their class.

Next, cranks were ordered from the leading German specialist, Hirth, who also supplied Gilera. Roller cranks were still thought best for racing motorcycles. The open question was, is it stronger to use a built-up crank with one-piece rods and non-split bearing cages? Or is it stronger to use a one-piece crank with split bearings and rods? Great 1930s rivals Mercedes and Auto Union had stood on opposite sides of this choice, each tempted by problems to try the other’s solution.

The usual built-up crank is made by press-fitting crankpins into the flywheels, but pressed joints—even when assembled with tons of pressure—creep apart under high-frequency vibration. The Hirth assembly system consisted of radial face splines cut into one end of a hollow crankpin and into its mating flywheel. Once the one-piece connecting rod and its big-end cage and rollers were in place, pin and flywheel were powerfully drawn against one another by a large internal bolt, whose threads in the pin were of different pitch from those in the flywheel. If this seems arcane, consider that the 2800-cubic-inch piston engines on Martin and Convair airliners of the 1950s had cranks built in the same way.

To make the Hirth couplings strong enough, crankpin diameter had to increase by about 50 percent, to 30mm. This, in turn, resulted in a hefty assembly of sixteen 5mm con-rod rollers and their cage. As a crank turns, the speed of a crankpin bearing varies as the rod swings forward and back around the wristpin. This twice-per-revolution variation can be too much for a heavy roller assembly to follow. The result can be skidding, overheating and failure. To reduce the speed variation, the con rods were made exceptionally long, with a 2.6:1 rod ratio.

Carburetion was another issue. Eight magnesium Dell’Orto 20mm carbs, cast and machined by Guzzi, lived in the cylinder Vee like interlaced fingers. At first they were served by two float chambers on the left, but poor running soon forced provision of one tiny float chamber for each carb.

Guzzi's fairings were made by a remarkable craftsman who annealed the magnesium material between hammer-forming sessions by covering it with soap, then heating it until a certain color change occurred, showing that the hammer-hardened metal was again soft. All exhaust pipes were the province of another specialist who filled them with sand, its internal pressure adjusted from time to time by taps on tapered pins as the metal was made to yield by wise application of a torch flame. Try learning that from a drop-down menu.

Giulio Cesare Carcano and his assistant Enrico Cantoni

Giulio Cesare Carcano (middle) and his assistant Enrico Cantoni (right)

By December, 1956, the V8 program seemed back on the rails, its problems behind it. Power was good at 72 rear-wheel hp, with ability to pull from 7000 rpm. The 1957 season started well, with an Italian Championship win and another at the Imola Gold Cup. At the German GP, Dickie Dale came fourth (behind two Gilera Fours and Walter Zeller on a BMW Twin!) while teammate Keith Campbell retired with a silent engine. Dale and Campbell were fourth and fifth at the TT, Dale running 240 of the punishing 300-odd miles on seven cylinders. Ignition was by coil and battery, for the V8’s need of 800 sparks per second was beyond the era’s magneto ability. The two circular objects on the left ends of the V8’s intake cams each contain four sets of mechanical contact-breakers. Ten years later, Honda would need 900 sparks per second for its 250 Six and would get them from a Kokusan magneto.

There followed crashes, a lap record at Spa, a broken battery wire and controversy over handling. By Monza, there were two bikes ready on stands with no one willing or able left to ride them.

How did an old company, vastly experienced and successful in racing, come to this? The first point is that high-rpm problems were new to Guzzi, whose greatest successes came with moderate-revving Singles. Precious time was wasted using crank solutions already marginal on 8000-rpm Singles, and more time was lost having better cranks built. Had Guzzi continued racing rather than withdrawing with Mondial and Gilera in 1957, Carcano had planned a one-piece, plain-insert-bearing crank of the modern type recently adopted by Ferrari. All modern F-1 and MotoGP engines have cranks of this kind. Testing is the key to reliability in racing, and Guzzi’s fits and starts show it did too little. The European postwar motorcycle boom was ending, and racing was hard to justify

Secondly, there’s the unique nature of the 500 class. Chassis and suspension solutions that work well in 250 and 350 racing may bring disaster in the 500 class, as Honda’s RC-181 would reveal in 1966-67. MV, with years of 500 handling evolution behind them, amassed points while the Honda wobbled, punished its tires and suffered mechanical DNFs. Five-hundred experience counts! Guzzi lacked it.

Although other writers respectfully tiptoe around this, Guzzi’s riders were leery or even fearful of the V8’s handling. Look at the fairing-off photo to see how far back in the chassis the engine is. In that “hard rubber” era (the words of Dunlop veteran Tony Mills), engines were moved back “to increase traction” (the opposite of what had worked for Norton), but the real effect was to unweight the front, robbing it of tire damping, allowing high-speed weave to develop.

Experience is expensive and takes time. Gilera in the early ’50s had to swallow the embarrassment of seeing its new four-cylinder beaten again and again by single-cylinder Nortons! Gilera gave up cherished suspension ideas, stiffened its chassis and developed its engine until the company dominated 500 racing. Beginning in 1948, this was a five-year process. MV followed the same path—because there is no other.

Guzzi jumped in at the deep end with much to learn and lacked the time in which to complete the process. With its manageable weight of 330 lb. (exactly what four-cylinder MotoGP bikes weigh today) and a real potential for 90 hp at 14,000 rpm, the V8 might in 1958 or ’59 have had its day in the sun. Tires would remain narrow and hard until change was forced by the 1972 coming of 100-hp Kawasaki and Suzuki two-strokes to Daytona. The Guzzi V8 rolled on 2.75 x 19-inch front and 3.00 x 20-in. rear tires.

Here it is: The Gilera and MV Fours sat at the top of 500 racing in their respective eras, essentially without competition, doing just enough development to keep their riders from complaining too much (not complaining is incompatible with a living rider). Change requires force, and Guzzi’s Ing. Carcano applied it boldly, taking up complexity, cylinder multiplication and super rpm as his tools. Guzzi failed in the attempt, but its direction was correct. It would now be up to Honda to make the revolution Guzzi had begun.

Otto Cilindri: Moto Guzzi V8 Grand Prix Racer

Otto Cilindri: Moto Guzzi V8 Grand Prix Racer

Moto Guzzi V8 front profile

Evidence of the Moto Guzzi V8?s narrowness and small frontal area

Moto Guzzi V8?s narrow frame

Moto Guzzi V8?s narrow frame

Moto Guzzi V8 engine

Moto Guzzi V8 engine

Moto Guzzi V8 Grand Prix Racer sketch

Before the V8?s debut, Carcano gave the press this wheels-within-wheels drawing

Giulio Cesare Carcano and his assistant Enrico Cantoni

Giulio Cesare Carcano (middle) and his assistant Enrico Cantoni (right)

View of the Moto Guzzi V8's large oil-carrying frame backbone tube

View of the Moto Guzzi V8's large oil-carrying frame backbone tube