The salt can play tricks on you. Stare into the emptiness that surrounds Bonneville, Utah’s famed land speed record spot and you run the risk of seeing things that might not be there – hints of a phantom city obscured in the distance, the sun glinting off the flats at just the right angle to suggest that the barren waste around you goes on forever, or pools of water that confuse you into thinking you have somehow been transported back in time to stand on the surface of the vast inland ocean that once occupied this very spot.
If you’d popped the hood of a certain 1967 Chevrolet Nova wagon at this year’s Bonneville festivities, you would have sworn that the salt was messing with your mind on a much…smaller scale. Where one would expect to find a big-cube V8 – or at the very least a blown six-cylinder mill of some variety – instead, tucked at the very back of the gaping engine bay, sits a 60-cubic inch rotary motor.
From an Australian Mazda.
‘When we went to the rulebook, it was pretty clear that we wouldn’t be fast in the wagon running a V8,” said Dave Melott, who built the Nova with his partner, Scott Harrison. “So we took a look at G Class, and it just jumped out at us that we could be pretty competitive if we stuffed a rotary in there instead. It’s a lot of fun to see people’s reactions when they look inside the car – that little spinner is just 18-inches square.”
It’s the kind of logical leap that makes Bonneville Speed Week such an incredible gathering for gearheads: the decision to cross an ocean and ditch cylinders altogether in favor of a 50 year-old rotary spinning at 10,500 rpm inside a hunk of old Detroit iron. If you think that Melott and Harrison, both fabricators, went the rotary route because it was somehow ‘easier’ than building a big-displacement push-rod mill, well, you’d be mistaken.
“Between the two of us, we’ve always got about a dozen hot rods on the go, and the Nova was sitting in the back of a barn just waiting for us to tear out its 383 stroker. It was about three-quarters of the way to being a drag car already, so we figured it made a good starting point for the Bonneville build – but then we found out just how tough it was to going to be to actually find the rotary motor that we needed,’ Melott admitted.
The Mazda 10A unit that ended up in the Nova was eventually sourced from a late-60s Mazda R100, an early coupe that was popular in the Australian market. Given their background – Melott comes from the drag world, while Harrison has extensive experience building Baja trucks – the pair decided to stay within their comfort zone, slapping a Holley 850 carb on the motor and then porting the motor to within an inch of its life.
“These engines are really so simple that there’s not much you can do with them, aside from port work,’ said Melott. The 10A in the Nova has by now been bridge ported, which means not only has the original intake port on the motor been altered, but an additional ‘eyebrow,’ or arched slit port has been added just above it, creating a ‘bridge’ in between. This modification is a big piece of the puzzle when running above 10,000 rpm, as airflow is dramatically improved without having to worry about losing the rotor’s corner seals as they pass over the dual ports. A five-speed manual transmission corrals the 135 wheel horsepower produced by the motor, and while the Nova originally ran 5.10 gears this year a 3.60 setup yielded the best results.
After initially building the car in 2012 the pair set a record of 94.775 miles per hour the following year, but further work on the car yielded a new record of 106.948 miles per hour in 2016 – an impressive accomplishment from such an unusual, yet well-built salt rig. Due to the unique operating properties of rotary designs, however, the 60 cubic inch engine was subject to a ‘multiplier’ of two at Bonneville, with Speed Week rules placing it in the same class as 120 cubic inch piston engines. Although both Scott and Dave plan to keep running the high-rpm Nova on the salt, Melott isn’t optimistic that the car will continue to be competitive in G Class as time marches on.
“We’re at the point now where to get much more speed out of the car, we’re going to invest a substantial sum of money,” Melott told us. “We’re definitely not going to stop working on it, as we think there’s more speed locked up inside, but that correction factor is starting to look like a pretty steep hill to climb.
After spending years on the salt, it’s good to know that Melott and Harrison will be back in 2017 to defend their G-Class title – and that they’ll be bringing their just-as-original pusher truck with them, too.
“The ’39 International is a lot of fun, too,” said Melott. “It’s a project we had around the shop, and as you might be able to tell, we’re both all about building something that’s a bit different from what you normally see at Bonneville.” A chop top International rat rod certainly fits that description to a T – especially when it’s hauling around a Nova wagon with a JDM heart.
Instead of pistons going up-and-down as in a traditional internal combustion engine, rotary–more accurately called Wankel, after Felix Wankel who patented the first one–engines have one (or two, or three) triangular rotors inside that spin in response to the combustion of fuel. Rotors are contained inside housing chambers, and have three points – each one constantly making a seal with the housing. As a rotor turns it goes through the intake, compression, ignition, and exhaust cycle just like a piston motor, only it does so while spinning in an eccentric pattern inside the housing and transmitting power though an eccentric shaft.
Because there are really only a handful of lightweight moving parts – the rotor(s) and the shaft – Wankel motors can spin extremely quickly. It’s also a bit tricky to accurately calculate a rotary motor’s displacement, as you can’t just throw bore area, stroke, and the number cylinders into a spreadsheet and hit the ‘multiply’ button. Instead, you have to consider the swept volume of each of a rotor’s three faces, and the fact that unlike a 4-cycle piston engine, the rotor doesn’t need two crankshaft revolutions for each full thermodynamic cycle. With a pair of rotors in the picture, off-set at 180 degrees, you get two rotor faces completing a combustion cycle in a single crankshaft rotation. Two crankshaft rotations would see four faces completing a cycle – roughly equivalent to what a piston engine needs to achieve its single cycle. This is why a multiplier of two is frequently applied to rotary engines in motorsports to correct for ‘volume’ in comparison to a piston design.
Rotary fans can argue all day about the pros of going “pistonless,” and the design does allow for high RPM, less mechanical parts, and a small, light, engine package. The negatives include efficiency (not very) and poor mpg, and lack of torque.