When it comes to custom engine builds, we've seen almost everything. But taking a standard pushrod V8 and completely reversing its airflow? That's the kind of mad science that makes the internet stop and watch.Calvin from Nivlac57 recently took on a project that sparked a lot of skepticism: a "Hot V" LT/LS engine build. The premise is simple but mechanically terrifying—they wanted to flow the engine backwards. The exhaust ports became the intake ports, and the intake ports became the exhaust. Instead of the exhaust routing down the sides of the block, it now exits right out of the middle of the "V", and the intake manifolds sit on the outside.The biggest questions from the start were obvious: Will it work? Will it immediately break? Will it even rev past 5,500 RPM? And most importantly, will it sound cool?AdvertisementAdvertisementWe finally have the answers.Fabricating the ImpossibleReversing the flow of an engine isn't as simple as just bolting the manifolds on backward. Calvin had to fabricate completely custom intake manifolds from scratch. This involved milling precise pockets to weld in injector bungs and fabricating custom fuel rail hold-down brackets."This is kind of a tedious process because you need to be kind of careful with how you manage the heat in order to not melt into the machined surface that the injector O-ring needs to seal against," Calvin noted. "But you're also welding a thick material to a very thin material."They also ran into a classic GM parts bin issue: the rocker ratios. The LS engine uses a 1.7 rocker ratio, while the LT uses a 1.8. Because of this, their 0.585 lift camshaft effectively became a 0.619 lift cam, forcing them to upgrade to heavy-duty 0.660 lift springs from Tick Performance before startup.But controlling an unconventional setup with two massive throttle bodies sitting on the outside of the engine was going to be a nightmare with standard drive-by-cable throttle bodies. The solution came via a Holley Dominator ECU.AdvertisementAdvertisement"It supports dual drive-by-wire control," Calvin explained. "How this works is you have one plug here that goes to your single pedal in the car, and then you have two throttle body outputs… It takes the command from this one throttle pedal and commands two throttle bodies to open. This is going to be way cleaner than having to come up with some sort of apparatus to control two drive-by-cable throttles."With a set of Bosch 210 lb injectors and a Holley drop-in dual 450 LPH fuel pump setup, the engine was prepped to eventually run on methanol or heavy E85.The Startup and the 6,800 RPM ScreamAfter evicting a stubborn mouse that had taken up residence on the lathe and sealing the custom manifolds, it was time to fire the "Hot V" up.Running an engine backward means you can't just expect a base tune to work perfectly out of the box. During the initial cranking, the engine was running incredibly rich. "I would expect this to take a little less fuel than normal because of the intake valves… you can see the fuel coming out the exhaust," Calvin noted, quickly pulling 20% of the fuel out of the map.Once the fuel curve was adjusted, the engine roared to life, and it sounded mean. The reversed flow gives the V8 a uniquely tight, aggressive exhaust note. But the real test was the rev check.AdvertisementAdvertisement"That was 6,800!" Calvin's shop partner exclaimed after a massive rev. The engine wrapped up instantly, proving that the reversed flow and smaller intake valves weren't choking the engine out at the top end. "That thing wraps fast… small valves, yep, that's torquey," they confirmed.The proof of concept is officially a success. Nivlac57 proved a backward-flowing LS/LT can run, rev to the moon, and sound incredible doing it. But this was naturally aspirated. The true goal of the Hot V setup is forced induction."The next time that you guys see this, it will have turbos, and hopefully we can run this thing down the road or at least do a burnout in the driveway," Calvin promised.Well, we'll be watching Calvin.