The Ford V8-powered Monster Miatas are fun, freaky little cars, but there is room for improvement in the horsepower and torque provided by the old 5.0 powerplant. Stuffing an LS3 Corvette engine in a Miata is awesome, and the guys over at Flyin’ Miata have done just that. Their site features a step-by-step build of the LS3 powered Miata complete with pictures.
One would think that converting an innocuous little Miata to a V8 powered street machine would add tons of weight and spoil the balance of the car. According to Flyin’ Miata site, the conversion only adds 200 pounds to the overall weight, with approximately 1/3 of the additional heft over the rear wheels. With 480 horsepower from the GM Performance Parts LS3 with a hot cam, the addition seems minor indeed.
There are necessary modifications in order for everything to work properly, but once it is done you are left with a sleeper. The transformation of the ’99 Miata from a 1.8L 4-cylinder to a ‘Vette powered beast requires some cutting, welding and tweaking a few parts, but the end result is sweet.
So the best place to start is to dive on in and carefully gut the car. Once the dash and carpet are removed for the modification of the tunnel, it is game on for the swap. Although it is not necessary to reshape the tunnel due to the availability of aftermarket kits, the balance of the car can be upset through their use. The aftermarket kits push the powertrain too far forward for the Flyin’ Miata guys’ tastes. Instead, the tunnel is reshaped to accommodate the T56 six-speed transmission and to prevent distorting the balance of the car. A unique piece added to the car during this stage of the build are the “Frog Arms,” which provide much needed to rigidity to the front of the Miata.
Next in line for installation are a new subframe, frame rails, transmission cross-member and differential mount bracket. V8 Roadsters sells a variety of parts designed for projects like the LS3 Miata.
Despite the well-labeled wiring harness that comes with the GM Performance Parts LS3 engine and the ease of the throttle pedal installation, the oil pan presented a problem. Clearance issues led to the use of a modified F-Body oil pan.
The wiring harness was lengthened and the ECU was cleverly mounted inside the car. After finishing up the wiring and mounting, the exhaust was added which brought about another modification. It may seem as though the word “modification,” is used to death during this process, but in reality it is a necessary evil and is reflective of just about any swap story. This time it was necessary to make a slight indentation in a header tube for the steering shaft to have proper clearance.
All that was remained were the power steering brackets, the air conditioning brackets and a set of custom gauges. Following the completion of the swap was the mandatory trip to the dyno. Originally the ’99 made 121.2 horsepower and 114.2 ft-lbs of torque, but with the newly installed GM Performance Products LS3 the ’99 laid down 414.7 horsepower and 430 ft-lbs of torque.
With all of the additional power you might expect the car’s handling capabilities to be compromised, but this is not the case. “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…” – a direct quote from the Flyin’ Miata website.
The completed project has the appearance of a stock Miata, but once started there is no way to confuse the sound of LS3 and the puny four-cylinder. Corvette power with the handling and balance of a Miata makes this one fun little car.
