There are three levels of upgrades, and the top one boasts 1,001 bhp.
The McLaren 600LT's production only lasts 12 months, but Hennessey now offers power upgrades for the limited-run, hardcore model for any owners who want to give their rare machine a big increase in output. In the top HPE1000 trim, the 3.8-litre twin-turbo V8 makes 1,001 bhp and 865 pound-feet of torque, rather than the stock figures of 592 bhp and 457 lb-ft.
Gallery: 2019 McLaren 600LT: First Drive
"I decided to buy my 600LT for the same reason I bought a new Ford GT to give our team a solid benchmark for our Venom F5," company boss John Hennessey told Top Gear. After driving the McLaren, he decided it was "asking for more power" and had his team get to work on upgrades. Hennessey thinks the 600LT with the HPE1000 could be a performance threat to the McLaren Speedtail hypercar.
To obtain such a significant power upgrade for the 600LT, Hennessey installs revised turbos, a high-flow wastegate, new exhaust hardware, an upgraded intercooler, high-flow air filters, and Motec engine management. Tweaks to the seven-speed gearbox make sure the transmission is strong enough to handle the extra muscle.
Hennessey claims that a 600LT with the HPE1000 package can reach 60 miles per hour in 2.1 seconds and cover the quarter mile in 9.6 seconds. A stock example of the McLaren hits 60 mph in 2.8 seconds.
Hennessey also offers less powerful tunes for the 600LT. The HPE 800 pack bumps the output to 805 bhp and 722 lb-ft. The company claims it gets to 60 mph in 2.4 seconds and sprints through the quarter mile in 10.1 seconds.
There's also the HPE 700 version with 708 bhp and 635 lb-ft. Reaching 60 mph requires 2.6 seconds, and a run through the quarter mile takes 10.5 seconds.
Hennessey doesn't offer pricing for these packages. However, owners can afford a 600LT's base price of £185,000, then they probably aren't too worried about spending a little more to boost their new car's performance to hypercar levels.