What the 1978 Jaguar XJ-S Group 44 Trans-Am was

The 1978 Jaguar XJ-S Group 44 Trans-Am was a race-prepared version of Jaguar's luxury coupe, built by Group 44 Inc.—an American racing team based in Virginia—specifically to compete in the IMSA Trans-Am series. Unlike the street XJ-S that buyers could purchase from dealers, this car was stripped of sound deadening, fitted with a modified 5.3-liter V12 engine producing around 600 horsepower, and equipped with racing suspension, brakes, and a roll cage. Only a handful were ever built, making it one of the rarest and most significant racing Jaguars of the 1970s.

Group 44, led by driver and team owner Bob Tullius, had already established itself as a top racing outfit. The Trans-Am series at that time was one of North America's most competitive racing categories, and Jaguar's decision to enter with Group 44 represented a serious factory-backed effort. The car competed against Chevrolet Camaros, Pontiac Firebirds, and other American muscle cars—a notable contrast to Jaguar's traditional image as a maker of refined British sports cars.

Key Takeaways

  • The 1978 Group 44 XJ-S was a race-only car built for IMSA Trans-Am competition, not a street-legal production model.
  • Group 44 modified the standard XJ-S with a 600-horsepower V12, racing suspension, and a full roll cage for track use.
  • Very few examples were built, and most surviving cars are now owned by collectors or museums rather than driven regularly.
  • Maintenance and repair of a 1978 Group 44 XJ-S requires knowledge of both classic Jaguar systems and period race car engineering.
  • Parts sourcing is difficult because the car was never mass-produced and many original racing components are no longer manufactured.

Engine and fuel system maintenance

The 1978 Group 44 XJ-S retained the Jaguar V12 engine as its foundation, but Group 44's modifications changed how it ran and what it needed. The engine was bored and stroked, fitted with a different camshaft, and fed by a modified fuel system designed to handle the higher output. If you own or maintain one of these cars, you need a mechanic familiar with both classic Jaguar V12s and race engine tuning—not every shop that works on XJ-S models will have that informed.

Fuel system work is particularly important because the original racing fuel system may have used components that are now obsolete or unsafe by modern standards. The carburetor or fuel injection setup (depending on which specific car you're looking at) should be inspected by someone who understands period racing fuel delivery. Fuel lines, filters, and the fuel pump all degrade over time, and a failure during operation can be dangerous. If the car has been sitting, the fuel tank should be drained, cleaned, and inspected before the engine is run again.

Cooling system and radiator work

The V12 engine produces significant heat, and a race car's cooling system is engineered differently than a street car's. The 1978 Group 44 XJ-S likely has a modified radiator, possibly a larger capacity unit or one with different fin spacing to handle sustained high-temperature operation. The cooling fan, water pump, and thermostat are all critical to preventing overheating, which can cause catastrophic engine damage in a V12.

Before running the car, have the cooling system flushed and refilled with fresh coolant. Check all hoses for cracks, leaks, or deterioration—rubber hoses from the 1970s are particularly prone to failure after decades of sitting. The radiator itself should be inspected for internal corrosion or blockages. If the car will be driven or displayed, consider having the radiator professionally rodded out (cleaned internally) to restore full cooling capacity.

Brake system inspection and restoration

A race car's brakes are engineered for extreme duty, and the 1978 Group 44 XJ-S almost certainly has upgraded brake components compared to a street XJ-S. The brake lines, master cylinder, calipers, and pads are all designed to handle repeated hard stops and high temperatures. After decades of storage, the brake fluid will have absorbed moisture and degraded, and the system may have internal corrosion or air in the lines.

Do not attempt to drive this car without a complete brake system inspection. Have a may have access to mechanic flush the entire system, replace the brake fluid, and inspect every component for leaks or damage. The brake pads and rotors should be examined for wear and replaced if necessary. If the car has been stored outdoors or in a damp environment, the calipers may need to be rebuilt or replaced. Test the brakes thoroughly in a safe, controlled environment before any road use.

Suspension, steering, and chassis work

The Group 44 modifications included a race-tuned suspension with stiffer springs, different shock absorbers, and possibly modified control arms or anti-roll bars. These changes make the car handle differently than a stock XJ-S, but they also mean that standard suspension parts may not be correct replacements. The steering system, tie rods, and ball joints all need inspection because they bear the stress of high-performance driving.

Have the suspension checked by a mechanic who understands both classic Jaguars and race car geometry. The bushings—rubber components that connect suspension parts—often deteriorate and should be replaced if they show cracks or excessive movement. The shock absorbers should be tested to confirm they still provide proper damping. If the car will be driven, a four-wheel alignment is essential to may support safe handling and even tire wear.

Electrical system and wiring harness

The 1978 Group 44 XJ-S has a 1970s-era electrical system that may have been modified for racing. The wiring harness, battery, alternator, and starter all age and degrade over time, especially if the car has been stored. Rodents may have chewed through wires, and corrosion can develop inside connectors. The original wiring insulation becomes brittle and can crack, creating fire hazards.

Before powering up the car, have the entire electrical system inspected. Check the battery terminals for corrosion and replace the battery if it has been sitting for more than a few years. Inspect the wiring harness visually for damage, and have a mechanic test the alternator and starter. If the car has been stored in a damp location, consider having the wiring harness professionally tested with a multimeter to identify any shorts or grounds that could cause fires.

Fuel tank and fuel system safety

Race cars often have fuel cells—specialized tanks designed to prevent fuel leaks during crashes and high-speed maneuvers—rather than the original production fuel tank. If the 1978 Group 44 XJ-S has a fuel cell, it should be inspected for leaks, cracks, or deterioration of the internal bladder. Fuel cells have a service life and may need replacement if they are more than 20 to 30 years old, depending on storage conditions and use.

If the car still has the original production fuel tank, it should be removed, drained, and inspected internally for rust and sediment. A fuel tank that has been sitting for decades may have significant internal corrosion that can clog fuel filters and damage the fuel pump. Professional fuel tank cleaning services can restore an old tank, but replacement may be safer and more reliable if the tank is severely corroded.

Documentation and parts sourcing challenges

One of the biggest challenges in maintaining a 1978 Group 44 XJ-S is finding parts and documentation. This car was never mass-produced, and many of the racing components Group 44 installed are no longer manufactured. Original Jaguar XJ-S parts are still available from specialty suppliers, but race-specific modifications may require custom fabrication or sourcing from other racing teams or collectors.

Before undertaking major work, try to locate the car's original build documentation or racing history. This information can tell you exactly what modifications were made and what parts were used. Contact Group 44 directly if possible, or reach out to Jaguar clubs and race car collector groups—they often have members with knowledge of specific cars. Having accurate documentation makes repairs easier and helps preserve the car's historical value.

Frequently Asked Questions

Can I drive a 1978 Group 44 XJ-S on public roads?

That depends on whether the specific car has been street-legal registered and what modifications remain. Most Group 44 race cars were never street-legal and would require extensive work to meet modern emissions and safety standards. Check your local vehicle registration requirements and consult a mechanic before assuming any road use is possible.

Where can I find parts for this car?

Original Jaguar XJ-S parts come from specialty suppliers like SNG Barratt or Coventry Climax, but race-specific components are harder to source. Contact Jaguar clubs, IMSA racing historians, and classic race car specialists. Some parts may need to be custom-fabricated by a machine shop familiar with 1970s race engineering.

How much does it cost to restore a 1978 Group 44 XJ-S?

Restoration costs vary widely depending on the car's condition and how extensively you want to restore it. A basic mechanical restoration to get the car running safely could cost tens of thousands of dollars. A full concours restoration to racing condition could cost significantly more. Get detailed estimates from specialists before committing to work.

Should I store this car indoors or outdoors?

Always store a 1978 Group 44 XJ-S indoors in a dry, climate-controlled space if possible. Outdoor storage accelerates rust, corrosion, and deterioration of rubber and electrical components. If indoor storage is not available, use a high-quality car cover and may support the storage area has good ventilation to prevent moisture buildup.

What should I do before starting the engine after long storage?

Do not start the engine without first checking the oil level and condition, inspecting the cooling system, and confirming the battery has charge. Change the oil and filter, flush the fuel system, and have the brakes inspected. Start the engine only in a well-ventilated space and listen for unusual noises. Run it at low RPM for a short time, then shut it down and inspect for leaks before attempting any driving.