By now most of us are familiar with GM’s Gen. V LT5 V8 made famous by the outgoing C7 Corvette ZR1. In the Corvette, the 6.2L small-block cracked out 755 horsepower and 715 lb.-ft. of torque, thanks to a larger supercharger compared to the 6.2L LT4 it was derived from, along with the addition of both port and direct injection. Which makes this carbureted LT5 V8 featured by LSX Magazine all the more superlative.
The folks down at United Speed World in Tampa Bay, Florida, have built a version of GM’s most powerful production small-block V8 with a carburetor. Yes, a carburetor. It’s actually quite a feat to take such a technologically advanced engine and transform it into a big fuel funnel. USW dubs it the LS/LT. Let’s have a listen:
For some perspective: the LT5 was GM’s first attempt at dual-fuel injection, and it delivers more than 2,000 psi of high-pressure fuel to the injectors via a cam-driven mechanical fuel pump. The cam-in-block is equipped with variable valve timing which allows duration to move from mild to wild giving the LT5 even more power at the top end of its rev range. Like most modern engines all of this complex engine logic is monitored by a battalion of sensors directed by the PCM.
In ditching the supercharger an appropriate intake manifold would have to be found, obviously, there’s no carbureted LT5 intake manifold readily available, so one was adapted. Holley’s LS3 carburetor-ready intake was chosen along with ICT Billet intake adaptors to get the Gen IV LS3 intake to play nice with the Gen V LT heads. In order to simplify things further, the VVT was locked out using a lockout kit from Comp Cams’ and a cam sensor adaptor harness, again from ICT Billet. With the stock PCM tossed, an MSD 6LS box controls the ignition system.
The next hurdle to overcome would be the LT5’s dual-fuel system. In fact, it would be eliminated altogether. The fix was relatively simple, just yank the injectors and use a set of Motion Raceworks injector delete plugs paired with ICT Billet’s delete plug hold down brackets. The last major change was swapping the LT5’s stock water pump for a centrally mounted LS version. The LT’s use an offset pump, but because USW deleted almost the entire accessory drive, the water pump was free to relocate to a more aesthetic position via Dirty Dingo adaptors.
As for the numbers, the now carbureted LT5 makes 501 horsepower at 6,500 rpm and 446 lb.-ft. of torque at 5,500 rpm on pump gas and a relatively mild 10.0:1 compression ratio. The LT5 was never going to make as much power missing its big 2.65L blower, but this is still impressive jam.
At the end of the day, sure USW could have just built another garden variety LS3 with a lumpy cam and called it a day. At least this carbureted LT5 is unique, it’s all but guaranteed you’re never going to run into another one like it out there. Plus, the thing just sounds downright nasty, and that’s really the most important thing.