V8 conversions

Conversion parts

The math is simple. Little car plus big engine = high performance. The trick is putting the big engine in without spoiling the little car.

We've teamed up with the experts at V8 Roadsters to offer a kit that mates the amazing GM Gen III/Gen IV - or "LS" - family of engines to a 1990-05 Miata. The engine is a beauty that ranges in size from 5.3 to 6.3 liters and makes a minimum of 300 hp and 300 ft-lbs with a wide range of upgrades available. We mate it to a strong T56 6-speed transmission that offers a nice tight gate and an extremely relaxed cruising gear. The rear end is an aluminum-bodied limited slip unit from the Cadillac CTS, with a custom driveshaft, new rear hubs and high-strength axles. Engine management is handled by the stock GM unit, which is easily reprogrammed and can return OBD-II codes.

To mount the engine, we have a fabricated tubular subframe that's 10 lbs lighter than stock. The transmission is supported by a brace that also reinforces the frame rails for extra rigidity. The engine is set back as far as possible to optimize the weight distribution, and some modifications are required to the engine bay and transmission tunnel. The Miata power steering is retained and you can use A/C and the front sway bar.

Overall, the car gains less than 200 lbs with 1/3 of that on the rear wheels. In other words, the car does not become a nose-heavy beast. To put things in perspective, one of our SuperFour Challenge turbo Miatas came in at almost exactly the same weight and distribution. From the outside, the car looks completely stock. The ground clearance is unchanged and nothing needs to be altered on the body. As long as the engine is off, it's a great sleeper. But once you fire it up, there's no mistaking what's underhood.

Does it handle? Well, the first time we took one autocrossing, we set FTD with it - by a margin of nearly 4 seconds. We've destroyed our own lap records around our local track, outrunning purpose-built race Miatas with a street-oriented V8 Miata. Yeah, it handles.

Build diaries
Elvis, our own car. Including the build, autocrossing and modifications.
The green 1999. A 480 hp LS3? Of course. Completed.
The silver Mazdaspeed. 480? That's for wimps. This one goes to 500. Completed.
Geoff's car. "I don't want too much power", he said. Completed.
Dan's car. The first 1990-97 model to come out of the FM V8 doctor's office.
The Pi Car. Another NA goes under the knife.

Frequently Asked Questions
FMV8FAQ

Build information
Conversion parts - here's what you need.
Configurator - figure out how the options work.
Turn-key cars - drop your car off at FM and drive it home!
Home builds - we know that lots of people like to build their own, and we'll support you as best we can. Here's a list of all the parts you'll need to finish the job.