Jaguar XJ8 Gets LS3 Power

The Classy Jaguar XJ8 L

Teacher, author, entrepreneur, and recognized TED speaker Karl T. Muth recently shared with the world his awesome, customized LS3-powered 1999 Jaguar XJ8 L. According to Karl, this car delivers an outstanding 575 horsepower – making it the one of the most powerful documented Jags of its kind.

The Jaguar XJ8 (X308) is one of the great British classic cars that graced the turn of the new century; an exceptional full-size premium sedan that boasts timeless British styling and offers build quality and craftsmanship that is above that of most of the competitors of its time. It also offers inspiring levels of luxurious comfort and great performance. Its ride quality is also superb, even when driving on uneven road surfaces. This car delivers a refined and well-equipped interior with large, comfortable front seats that provide an excellent driving position and great visibility. Also worth noting is that Karl’s XJ8 is a long-wheelbase model, which means that it offers tons of rear legroom.

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The Awesome LS3 Engine

Karl’s initial intention was to install a stock CT525 6.2L LS3 crate engine from General Motors designed for high-performance cars. As it is, the CT525 crate engine is an outstanding, naturally aspirated racing engine that develops an impressive 525 horsepower at 6,600 rpm. However, Karl was looking to push the envelope a little further by customizing this engine to get more out of it, He drew inspiration from the supercharged LS9 engine of the Corvette ZR1 and also chose to re-machine certain components of the LS9 engine e.g. the cylinder heads and head gasket to suit the naturally aspirated CT525 engine. Karl also incorporated a Lingenfelter camshaft, sodium-filled exhaust valves, and titanium intake valves. These tweaks and customizations cranked up the power of this 6.2L LS3 crate engine to an amazing 575 HP.

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A Worthy Transmission to Match

To match this engine’s enhanced output and performance, Karl chose to install a custom-built T-56 Magnum manual transmission. The revered high-performance T-56 Magnum transmission has successfully been used on a variety of supercars like the Corvette ZR1 and the ACR Viper. It is a beefed version of the original T-56 manual transmission; all its gears, bearings, shafts, synchros, and forks are larger and heftier, and this enables it to handle the massive torque of the customized LS3 engine with ease. The T-56 Magnum that Karl fitted in his Jag had an exposed shift gate and was tuned with close shifting ratios. 

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Why The Jaguar XJ8 L is Just Right for the Customized CT525 Engine

On the outside, the luxurious Jaguar XJ8 appears to appeal to a more mature, elite, and dignified crowd, but behind the wheel, it reveals a more lively personality. The XJ8 is based on the platform of its more sedate previous generation i.e. the XJ40, but it is different from its predecessor in many aspects. The most distinct difference is the fact that the XJ8 comes fitted with a standard V8 engine. In Karl’s case, his XJ8 came fitted with a 4.0-liter V8 engine that smoothly delivered 290 horsepower. In addition to standard V8 power, the XJ8 also received subtle suspension and chassis enhancements that enabled it to match that kind of power. Karl’s XJ8 features an XJR Arden suspension that is tuned to deliver both comfort and the kind of sharp responsiveness that you want from a car that is driven by a 575-horsepower engine. On the road, the car feels solid and composed even at high speeds, and it offers excellent handling. Its cornering stability is also quite impressive; this can be attributed to its wide footprint and its low center of gravity. Another thing that is great about the Jaguar XJ8 is that it is rear-wheel-drive. This drivetrain helps to spread the load of the sedan across all four wheels, achieving an optimal weight balance that enhances handling and braking. It also helps to reduce wheel-spin when accelerating from a stop. With the incredible amount of power and torque that the customized LS3 engine produces, it is likely that if the car were front-wheel-drive, it would cause the driving wheels to spin considerably when launching from a standstill. However, because power and torque are sent to the rear wheels, the rear tires are jammed onto the road during acceleration, which results in enhanced traction and better acceleration.

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A Bargain!

All things considered, Karl’s Jaguar XJ8 L is indeed worthy of the mighty customized LS3 engine. Amazingly, Karl bought his 1999 Jaguar XJ8 L for only $1,201 on eBay, and despite its age, it had just 72,000 miles on the odometer. Talk about a bargain! Karl also went an extra mile to further refine his ride, replacing its analog instrument cluster with a Racepak digital instrumentation unit and adding Audi A4 front seats and a stock Alea-Leather-trimmed Jaguar rear seat. With all the modifications that he made to this car, Karl says that his expenditure went to just a little over $38,000. 

>>Join the conversation about the LS3 powered Jag right here in the LS1tech Forum!

For help keeping your Porsche running right, please see our how-to section in the forum.