Originally published in the NW Alfa Romeo Club newsletter, Iniezione, posted here with permission from the club.

One of the more intriguing aspects of our classic Alfas has, to me, always been their SPICA mechanical fuel injection system. Introduced in 1969 to comply with the USA’s latest emissions regulations, it was fitted only to Alfas, and almost exclusively only to Alfas sent to the USA.

Fuel injection wasn’t a new concept; it was first patented in 1872. Rudolf Diesel adapted it for his diesel engine in 1894 and most aero engines during WW2 were injected. All these were mechanical systems, and their potential for generating higher performance through better fuel atomization and more precise delivery also led to their use in racing cars (Mercedes-Benz, Corvettes, Alfas) and high-end road cars (MB again, Maserati, high-end BMW 2002s and Porsche 911s).

Introducing them to a full range of road cars, however, meant also exposing them to the full range of auto technicians across the country. It wasn’t that the SPICA system was complex – so are carburetors – but that it was different. It developed a reputation for being finicky and unreliable, but that was almost entirely due to being maladjusted by well-meaning but inexperienced technicians.

Its principal drawback was that, as a precision device made of very high-quality materials and built to very exacting standards, it was also very expensive to manufacture. When electrically-controlled systems became available at lower cost, Alfa quickly adopted them even though doing so cost them some performance. Over time, of course electronic injection and engine management systems in general have improved significantly and are now pretty much universal.

When I came across Harry White’s 1975 Spider at the AROC Winter Retreat in February 2024, I was intrigued to see that it had been fitted with a much more modern Alfa Twin Spark engine, but with a SPICA system replacing the Twin Spark’s standard electronic injection! Could it be that SPICA still had advantages today?

This of course led me to talk to Wes Ingram, who’d done the conversion, and I began to learn more about these fascinating devices. Wes’ initial observation was that “After restoring over 4,000 SPICA pumps we have learned so much, and we now find that they are far better than anyone ever realized when they were first presented to America in 1969.” In contrast to the one-dimensional wide-open-throttle race systems of the time such as Hilborn and Lucas, SPICA’s three-dimensional cam with temperature and altitude adjusters allowed for advanced and accurate fuel delivery management throughout the range of everyday street driving.

Wes remarked that the quality of design and manufacture in these pumps are so high that, if properly maintained and used, they just don’t break. “Proper use” means making sure that engine oil and filters are changed at the recommended intervals, and that the engine is regularly brought up to full operating temperature to drive off any accumulated moisture and condensation in the oil. As with the main car engine, you don’t want sludge and potential rust forming in a SPICA pump.

The cam is rotated about its axis by the throttle linkage. Pushing the throttle pedal down rotates the cam; its profile moves the stylus and so rotates the plungers to provide more fuel to meet the driver’s demand for power.

But remember that the cam is three-dimensional; it also moves horizontally as engine speed and load vary. This is achieved through six steel balls in a cup-shaped housing; as engine speed rises, the balls are flung outwards with ever-increasing centrifugal force, acting on the curved inside face of their housing to push the cam sideways and so move the stylus along the 3D profile to adjust the flow volume. Other adjustments are applied for altitude compensation (via an aneroid bellows) and temperature (to facilitate cold starts), as well as a deceleration fuel shut-off.

The end result is exceptionally precise fuel metering across the full range of engine needs: more fuel at higher rpm, less at idle and zero fuel during deceleration.  “Precise” in that the cam has over 3,000 specific metering points – Wes and Herb have mapped its profile on a test bench!

Each plunger forces fuel at 400 psi through a check valve and into the metal delivery line; the check valve prevents it flowing back into the barrel as the plunger descends for the next stroke. Fuel at 400 psi is thus delivered to the injector in the inlet manifold, where it’s held in check by a spring-loaded pintle valve; imagine a tiny poppet valve, like the inlet valve in the main cylinder head but in miniature. The pressure of the next delivery pulse from the pump plunger forces the pintle open, spraying fuel in an atomized cone (restricted by a shroud so that it doesn’t wet the inlet tract walls) until the pressure drops enough to let the pintle’s spring shut it off again. A disc with a tiny orifice is fitted in the input end of the injector to damp out oscillations in the fuel flow.

There’s enough internal volume in each injector and fuel line that, on average, fuel will be in them for something more than 10 engine revolutions, and up to as many as 100 at idle. This gives the fuel time to reach a temperature close to that of the engine coolant which surrounds the injector. The high pressure suppresses vapor formation inside the injector, but this means that the fuel charge, when released into the intake air passage, has high temperature as well as high pressure to assist with its atomization. The air volume in the inlet tract is similar to the swept volume of the cylinder and so doesn’t linger to get the same heat exposure; as a result, the engine runs with a cold air charge and a hot fuel charge. That’s pretty elegant.

As racers began to tune these engines with bigger valves and lumpier cams, improving their breathing at higher speeds beyond the road cars’ 5,800 rpm top end for which the original SPICA was designed, they began to find that the fueling was off at the higher engine speeds.

It wasn’t that the SPICA units couldn’t supply enough fuel; in fact, the standard cam profile was over-delivering fuel, beyond the engine’s ability to breathe well enough to use it. Over time, in addition to some painstakingly-developed custom grinds of the cam for modified engines based on Wes and Herb’s detailed mapping (e.g. bigger cams need more fuel where maximum torque occurs, 4,400-4,800 rpm), they found a way to use a supplemental spring to slow down the fuel increase at higher rpms. As a result, SPICA remains a very viable choice for both road and race cars, with precise fueling at all speeds.

As mentioned, well-maintained SPICA pumps are exceptionally reliable, but there was one problem that virtually all of them suffered in the early 1970s, when lead additives began to be phased out of our fuel. The plungers and barrels (P&Bs) in the SPICA pump are like miniature pistons and cylinders, but without sealing rings. All that keeps the fuel in the top separate from the oil in the bottom is the incredibly fine clearance between the plungers and barrels; it has to be less than the size of a gasoline molecule.

Made from very high quality materials, the P&Bs were designed to outlast the engine, and protected with high pressure engine oil and with additives in the fuel, they can. But when lead and sulfide additives were banned from fuel from 1970 on, the P&Bs began to wear and allow fuel to seep through into the oil and thus back into the main engine. Today’s unleaded fuels contain additives that are equal to or better than the old lead and sulfides, but the damage has probably already been done. You can smell it if you take an oil sample from the pump, or you can have the oil analyzed to make sure, but if you don’t take action your whole engine will wear prematurely.

Because new P&Bs are no longer available, Wes’ partner Herb Sanborn meticulously laps worn ones until they’re straight and true, then hand-matches them to find pairs with just the right clearance. This can only be done by hand, as the clearance is essentially unmeasurable. It’s incredibly painstaking and a real art, but once done, and with modern fuels, you should never have a problem again.

Finally, let’s take a look at the various improvements Wes and Herb have been able to make to the SPICA units over the years, which are all things the factory would have undoubtedly done if they’d continued with SPICA’s development.

• Upgraded cam follower stylus. This follower looks something like a ballpoint pen and moves with every movement of the throttle pedal, riding the surface of the 3-D cam to determine how much fuel the plungers deliver. The tiny .017” ball in its tip eventually sticks and develops a flat spot. Due to the leverage in the linkage, this has a noticeable effect on performance and emissions. Worse, the ball can suddenly rotate in its housing, abruptly moving off the flat spot and changing the fuel mixture again. All rebuilt SPICA pumps are fitted with an oversize ball in the tip of the follower, one that doesn’t stick or wear out.
• A timing mark on the drive belt pully. With no factory marking the belt was often fitted incorrectly, leading to inaccurate timing of the injection pulses.
• Higher-quality re-manufactured thermostatic actuators. Poor cold starting due to faulty units led many owners and mechanics to install a bypass switch to cut out the cold start solenoid, which led to its own problems. Better actuators have virtually eliminated cold-start problems.
• Replacement of the deceleration solenoid microswitch in its hard-to-reach location under the pump. Because the pump has to come off to reach it, this was often ignored in service.
• An improved technique for tightening the tiny screws clamping the gears to the pump plungers so they no longer work loose after high mileages. The plunger/gear sets are also calibrated to within 1% variation on a flow bench.
• Improved mounting of the spring on the tie-rod clip and fitting a damper spring inside the altitude compensator return spring, eliminating breakage from vibration for both.

I started looking into SPICA out of curiosity as to why someone would go to great lengths to replace the electronic injection on a Twin Spark engine with a mechanical SPICA system. I ended with a profound respect for its quality and performance. Alfa saved a lot of money when they switched to electronic fuel injection, but performance took a significant hit.

If you have a SPICA Alfa, treasure it; you have a real gem.

Jon Inge