Hell Yeah: Someone's Stuffing a 707-Horsepower Dodge Hellcat Engine in a Mazda Miata
This 1999 Mazda Miata is getting the heart of a 2017 Dodge Challenger Hellcat—good for over five times the power it had when it was new.
While they take a while to get to it in their vlogs (we really don't need to see your Harbor Freight run on camera, guys), they finally took the engine from a wrecked 2017 Dodge Challenger Hellcat with some help from their friend Jose in a cool time lapse. Jose is currently rebuilding a burnt Hellcat on his own D.I.Y Gang channel, so he's a good person to pitch in for this. They need to pluck out that golden 707-horsepower, 656 pound-feet Hellcat V-8, plus the Tremec TR-6060 six-speed manual transmission.
Meanwhile, the NB-generation Miata came with a 1.8-liter engine that made just 140 horsepower from the factory and was paired to a five-speed manual transmission. The Hellcat swap is going to have over five times the horsepower—and that's stock, before they mess with the engine at all.
[Skip to about 4:30 in for the Miata disassembly.]
They also had to pluck the rear end of the Miata out as well since its teeny tiny differential wouldn't handle the extra power. The rear differential will get replaced with a Ford 8.8 later on in the swap and the axles will be tossed for larger ones, as those parts will have no issues handling the extra power.
Being able to cart away the entire front axle—complete with the engine and transmission—on a pallet is pretty cool. They plan on upgrading the suspension to coilovers and already ordered a few beefier parts to handle the extra weight of the Hellcat V-8, so they won't actually be reusing most of those parts.
The KARR team picked up a new crossmember capable of holding the Hellcat engine from V8 Roadsters, a shop that specializes in Chevy V-8 swap parts but doesn't custom-make anything for the Hellcat as that swap hasn't blown up into a common thing yet.
Next, the interior comes out so they can widen the transmission tunnel. This isn't as easy as the ubiquitous Miata LS swap, as the Hellcat engine and transmission are just a bit too wide to fit in the engine bay and transmission tunnel as-is. The rear end then comes out of the car to fit the engine and transmission in place.
Finally, the car gets lowered down and, shockingly, it fits with seemingly little effort. The stock manifold is just a bit too large, though, so it has to come off for the engine to slide up into place.
They're down to the nitty gritty of making the crossmembers and everything work together, so expect more action in their later videos. They're replacing the Miata steering rack with a manual rack, but using their existing one to test fit everything.
The Hellcat engine sticks up a bit higher than the old Miata engine, so I don't think this will be too much of a covert sleeper once they're done. Either way, I love that it actually seems to fit and expect no less than fat burnouts all day soon. You can keep up with their full build on the KARR channel here.
[Correction: There's been some confusion about the year and power figures for this particular Miata, which I've now edited above. The video description lists it as a 1998, which could plausibly be its build date, but the first actual model year for the NB generation would have been 1999. Furthermore, the video as well as Motor1 listed an incorrect power figure for the engine they took out, as the NBs in the United States only came with a 140-hp 1.8-liter engine.]
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