Hennessey Is Building an 800 hp McLaren 600LT
The McLaren Senna is not just about horsepower, of course. There's a lot more that goes into it and you can read all about it here where I compare it to a Dodge Viper ACR (they're MUCH closer than you think). But if you've got your heart set on an 800 hp McLaren and you missed out on the Senna, Hennessey is happy to oblige.
If you aren't familiar with Hennessey, it is an aftermarket tuning company based in Texas that is no stranger to American cars like Corvettes, Camaros, Mustangs, and Challengers, and even tunes some trucks and SUVs. Hennessey also is a bit of a "boutique manufacturer". Its last car - the Venom GT - set multiple world speed records (some unofficial) and it was based on a Lotus Elise chassis with a modified twin-turbocharged version of the LS7 7.0 litre V8 in the C6 Chevrolet Corvette Z06.
In Hennessey speak, HPE800 typically means it will make at least 800 hp. Their HPE800 Camaro SS makes 804 hp. Their HPE800 Cadillac CTS-V makes 830 hp. Their HPE800 Mustang GT makes 808 hp. You get the picture. Now, they've announced that they will be building a modified version of the McLaren 600LT to be called the HPE800 which means that, in all likelihood, it will have more than 800 hp. That would put it above McLaren's own Super Series 720S with 710 hp and even the Ultimate Series Senna with 789 hp.
No details have been announced but this isn't the first time Hennessey has modified a McLaren. They previously took a McLaren's MP4-12C and offered an HPE800 version which had "over 800 hp." To reach that figure, Hennessey upgraded the intercooler, intake, and fueling system (likely injectors and pumps) and it added in their own titanium exhaust, engine computer, and new ball-bearing turbos. Other upgrades included external wastegates and blow-off valves, upgraded transmission cooler and clutches, and custom wheels and functional exterior aerodynamic bits.
Chances are, most of the engine modifications will carry over. The 600LT makes 592 hp (600 PS) and the MP4-12C made the exact same 592 hp out of the same McLaren twin-turbo 3.8 litre V8. Judging by the photos released, though, it doesn't look like Hennessey changed much (or anything) of the exterior, including even the wheels, but maybe Hennessey is keeping all changes under wraps and just hinting at the potential with the HPE800 moniker. Only time will tell.
Performance should at least match, if not exceed, the 720S. When tested by Car and Driver, the 720S did 0-60 mph in 2.7 seconds and 1/4 mile in 10.2 seconds at 145 mph. Pricing and release date haven't been announced yet so we'll have to wait and see. Keep in mind, though, that an HPE800 package for a relatively humble Corvette costs $55,000 USD, so this won't be cheap, but it will most certainly be a fraction of the price of the Senna, which was £750,000/$837,000 USD. But, as with every large aftermarket tuner, Hennessey offers their own warranty on their packages so there should at least be some peace of mind that comes with that.