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A Forgotten Monster - the Most Powerful Corvette Engine Nobody Cared About
We found ourselves in the year 1987, where one of the most powerful and fastest cars wasn't a Porsche, Ferrari, or Lamborghini. It was a Chevrolet Corvette with a tuned port injection 350 small block and twin turbos.

A Forgotten Monster - the Most Powerful Corvette Engine Nobody Cared About

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At specifics Chevrolet dealerships in America, you could choose the "RPO B2K" option on the order specification sheet. The B2K was a high-performance alternative to the standard Corvette offered by Callaway Cars between 1987 and 1991. The story is that Chevrolet approached Callaway to provide this kind of model after seeing the power output that the tuning company extracted from tuned twin turbos Alfa Romeo V6 engines. The vehicle came with the classic Chevrolet warranty and a one-year 12,000-mile (19,312 kilometers) warranty from Callaway Cars. The conversion cost an extra $26,995 over the price of a base model Corvette.

Basically, after production in Bowling Green, Kentucky, the vehicle would be sent off to Old Lyme, Connecticut, where the Callaway was based, to install twin turbochargers. As a result, this would transform the adequate power of the Corvette into absolute insanity.

A one-off Callaway twin-turbo Corvette would then go off to set a world record 254.76 mph (410.00 km/h) while being emissions compliant and air-conditioned. This happened on Ohio's Transportation Research Center track, making it the fastest road-going car at the time.

Now, let's go back a little bit to understand the origins of the Corvette B2K. It all begins with the C4 Corvette, which in 1986 wasn't a powerhouse as we know this model today. The L98 5.7-liter V8 found in the C4 was underwhelming with only 230 hp (233 ps), but the chassis itself was competitive for its time.

Unlike the previous generation's body-on-frame, the C4 was a unibody frame construction, while essential improvements to the braking and handling left one piece of the puzzle to be solved. Chief Corvette engineer Dave McLellan looked to solve this annoying issue by turbocharging the model. For this job, he needed a brilliant engineer that could be trusted. Enter Reeves Callaway, an aspiring race car driver who was now building turbo kits for Volkswagen and Alfa Romeo cars in his own garage.

By November 1986, the Callaway team had built their first initial prototype, called the twin-turbo B2K. The power unit of the B2K differs significantly from the factory L98 engine. The four-bolt main caps were splayed, which means that they were drilled at an angle to increase rigidity; a forged 1053 steel crankshaft and forged connecting rods replaced the cast rotating assembly, and the compression ratio was lowered with forged molle pistons. In order to maintain emissions compliance, the camshaft grind and cylinder heads remained factory.

However, the valve springs were swapped to ones with more seat pressure. Two turbochargers, oil, and water-cooled in twin air-to-air intercoolers, are attached to the power unit. As a result, the power output was 345 hp (350 ps) and 465 lb-ft (630 Nm) of torque. In addition, later revisions would get all the way up to 402 hp (407 ps) and 582 lb-ft of torque (789 Nm), which at that time was world-class power. However, even Callaway knew that wasn't enough.

As a result, in 1988, one specific B2K Corvette was taken to the extreme. We are talking about the chassis 1988-051, aka "Sledgehammer". The unique Corvette received a revised intake manifold and a throttle body to free up some high rpm power, and the turbo pressure was increased to a whopping 22 pounds of boost. All of this combined led to an output of 898 hp (906 ps) and 772 lb-ft (1046 Nm) of torque.

Reeves Callaway was adamant about retaining all the stock interior options of the B2K, such as the air conditioning, power seats, etc. The only addition was a roll cage and fire equipment. That's how the Sledgehammer set the record.

The C4 Callaway twin-turbo was also a good value proposition of money to performance than his European counterparts. It came in at considerably less money than the Porsche 911 Turbo, Ferrari Testarossa, or Lamborghini Countach. Also, as we said, the B2K package was nothing more than an engine modification, so the rest of the vehicle was just a regular Corvette. As a result, maintenance was very cheap.

So, given all the attributes, why did the Callaway C4 seemingly go under the radar? Well, first off, the added package wasn't cheap, starting at around $20,000 and ranging upwards to $30,000 on top of the price of a Corvette. If adjusted for inflation, it's almost $55,000 on top of a $60,000 Corvette which it's very costly. Also, the ability to produce vehicles as fast as they were being ordered was a nightmare, and out of the 400 plus orders, only around 125 were built by the company. As a result, the car is very rare. By 1990, the C4 ZR1 was out with similar performance and really put the nail in the coffin for the Callaway model.

The "Sledgehammer" and the Callaway Corvette carry a legacy of innovative engineering derived from old processes and technologies that can still be relevant and impressive.

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