LS-Swapped Miata is the Grown-Up Go Kart We Need in Our Lives

10 min read

LS-Swapped Miata is the Grown-Up Go Kart We Need in Our Lives

10 min read

Sometimes you have to just let the winds of fate steer the ship. For Ryan Hamilton, a welder and fabricator from South Kingstown, Rhode Island, that’s meant that the concept behind this first-gen Miata build has been a moving target ever since it rolled into his garage back in 2018. Some of that fluidity can also be attributed to Hamilton’s eclectic tastes and DIY approach, the latter of which has allowed the project to change and evolve as needed.

“Early on I was into motorcycles, and when I was 18 I got an RX-7,” he explains. “I did the whole rotary thing for a while and made it quick, but then I shifted my attention to Volkswagens. A few months after I got my GTI I ended up pulling the motor and building it up, but at the time, the Volkswagen platforms were kind of limited in terms of how far you could go with horsepower.”

Around that same time Hamilton was also playing around with engine swaps, he tells us. “I had a 2001 Audi A4 that I had swapped a V8 into, and my friend had this 1990 Mazda Miata that I’d always had my eye on. I’ve always liked that platform. It was in good shape and rust-free – which is a big deal over here on the East Coast – so I ended up trading him the A4 for the Miata.”

The Miata was set up for corner carving when Hamilton acquired the car in 2018, and he had initially planned to keep it dialed in for autocross events.

The car was dialed in for autocross when Hamilton took delivery, and he’d initially planned to keep it that way, albeit with a bit more grunt. “It had a 1.8 swap and I thought I’d just put a turbo on it or something like that,” he says. “And then I got the idea to do a K20 swap.”

But after figuring out what he’d need to get the Honda motor to work in the Mazda, he ran into a minor snag that would end up having a big impact on the build. “When I went to buy all the new parts online, the transaction wouldn’t go through. I called my bank and got it sorted out, but when I went back to do it again I had second thoughts. That’s when I realized that I actually wanted to put a V8 in this thing.”

After running the single-turbo LS setup for a year, the car went under the knife once again in pursuit of more boost.

The last-minute decision was aided by the fact that he had a line on a 5.3-liter LM7 motor from a Chevy Tahoe, along with a Nissan JK40 manual gearbox and the Collins adapter plate he’d need in order to make the combination work. The plan was to keep the car naturally aspirated and autocross-focused, so he sourced a Ford 8.8 IRS system from a Thunderbird and added a limited-slip differential, along with beefed up axles from Monster Miata.

“Once the motor was in the car, I was looking at clearances because I needed to make myself some headers,” he recalls. “It was going to be rough to make longtubes because of the packaging, and I decided it would just be easier to turbocharge it.” That led to a Borg Warner S480 single turbo setup with custom exhaust manifolds fabricated by Hamilton himself. Running on what he describes as a mild tune, he drove the car with that combination for a season before the urge to wrench on it struck again.

With some creative thinking and no shortage of fabrication by Hamilton – which included a tubular sub-frame modeled after the V8 Roadsters’ design – he was able to wedge the twin S480 turbo LS setup into the MX-5’s engine bay.

“It was around October of 2019 and I was sitting there looking at the car. I had this other turbo laying around and thought, ‘Hey – why not?’”

Adding another snail in the tight confines of the MX-5 engine bay was not a small task, though. “I had to sort of re-design some stuff to go twin. I re-did the front mount setup, too, and switched over to a 2-to-1 intercooler from Treadstone Performance. And of course I had to do a lot of work on the lines – I had go from a single oil feed line to a dual, make the drains, and I had to upgrade the fuel lines to 8AN.” A second Walbro 450 fuel pump was also added to handle the demands of the twin-turbo setup.

The rear suspension is currently an independent setup that was sourced from a Ford Thunderbird, but Hamilton plans to back-half the car and swap the IRS for a solid rear with a four-link as he continues to work toward a quarter-mile ET in the 8s.

Running about 18 pounds of boost and outfitted with ported L99 heads, a Sloppy Stage II cam, Siemens Deka 80lb injectors, a Sniper 92mm throttle body and a Holley Hi-Ram intake, Hamilton says the combo is good for about 700 horsepower. In a car that weighs roughly 2600 pounds, it equates to a power-to-weight ratio that’s on par with today’s most potent supercars, and Miata’s current aesthetic doesn’t make any attempt to hide the fact that it’s a potential giant-killer.

“I did a lot of research on high rise intakes and where they work best in the RPM range, and that design made a lot of sense to me for this build,” says Hamilton. “I also really liked the look of the Hi-Ram – it’s really sharp, aggressive. Along those same lines, the Sniper throttle body is just a quality piece. I’ve used cheap eBay throttle bodies in the past and they sucked. I’ve had zero issues with this one.”

Now that the powertrain is done – for now, at least – he’s turning his attention to the chassis. “While we wait for the snow to melt, I’ll probably re-do the cage and go from a 10-point to a 12-point. And since it’s a drag setup now, I’m going to back-half the car and swap out the IRS for a solid rear-end with a four-link setup.”

Looking further down the road, Hamilton has some ambitious targets set for the diminutive Mazda. “Eventually I’d like to get it into the 8s,” he says. “At that point I feel like I won’t have to do anything else to it. I’ll probably need a little more power to get there, so eventually I’ll probably build another LS for it, this time looking for about a thousand horsepower.”

He pauses for a moment to consider this. “The truth is, I just can’t leave things alone – I’ll probably the thing torn apart again before next summer is over.”


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