Meet the Mazda Roadpacer, the improbable merger of a GM Holden sedan and a Mazda rotary engine.
As you know, here at Mac’s Motor City Garage we strive to feature the strange and obscure in the automotive world. It’s only natural, then, that sooner or later we would have to get around to the Mazda Roadpacer AP—the inexplicable mashup of a Holden Premier sedan and a Mazda rotary engine. The AP stood for Anti-Pollution, oddly enough.
In 1975, Mazda of Japan was a struggling automaker eager to demonstrate that its development of the Wankel rotary engine was suited to a wide range of applications, from sports cars to light trucks. To create an entry for the executive sedan category in its home market, a showcase of sorts, Mazda arranged with General Motors of Australia to have semi-completed Holden HJ and HX sedans shipped to its Hiroshima plant, where they were fitted with Mazda 13B rotary engines and Nissan-Jatco three-speed automatic transmissions.
It wasn’t a happy combination. No synergy here. The 13B engine won many fans in the RX7 sports car and similar applications. But with 130 hp and only 102 lb-ft of torque at 4,000 rpm, the little rotary was a poor match with the mid-sized (by U.S. standards) Holden package with its 111-inch wheelbase and curb weight of 3,472 lbs, and the three-speed automatic didn’t help. Acceleration was horrible and fuel consumption was even worse: around 9 mpg, reportedly.
As if to compensate for the shortcomings, Mazda added a number of electronic gadgets to the Holden platform, including central locking and a dictation feature, and the upholstery was upgraded to plush velour. But on its exterior, the Mazda is indistinguishable from its Holden counterpart save for its badging and Japan-market fender mirrors.
Some 800 Roadpacers were produced between 1975 and 1977, although some models remained unsold as late as 1979. It’s said most went to the Japanese government. Auto writers like to note that the Roadpacer has the distinction of being the only GM production vehicle to be offered with a rotary engine. But this claim comes with an asterisk as the Roadpacer was a Mazda product, never sold under the GM banner. By the way, there was another, somewhat related Holden-Japan hybrid at around this time, the Isuzu Statesman De Ville, but that’s another story.
…and on a smaller scale (1/25, to be exact) there was a plastic model of a Chevrolet Vega with an optional rotary engine, which suggests that GM may have been at least thinking about the alternate power source.
GM went far beyond just thinking about a rotary engine. They reportedly paid between $40 million to $60 million – in 1970 dollars, no less – for the rights to Wankel/rotary patents. Many of us of a certain age can remember reading magazine articles promising a rotary engine powered Vega by 1973. Then 1974. And then 1975, in the Monza, and GM was to sell these power plants to AMC for the Pacer. But GM found, as many others did, that while the rotary offered a smaller size, fewer moving parts, and smoother running, the downside was increased wear, higher fuel consumption, and difficulty in meeting emissions standards. Not a good combination during a time of the OPEC oil embargo and tightening emissions standards.
It’s a shame that GM didn’t take all those millions and diverted them to a best-in-class fuel injection system, or to improving build quality during the 1970s.
We have access to a GM rotary prototype engine and plan to do a story on the program, hopefully sometime soon.
My family’s 1975 Buick Skyhawk (basically a Vega/Monza with a V6) had an abnormally tall transmission tunnel to make room for a rotary driveline. GM was pre-planning for a rotary future that never happened. This reminds me of the strangely-shaped firewall in big Dodge/Plymouth/Chryslers of the mid/late ’60’s and early ’70s which was the result of Chrysler’s planning for a possible turbine engine driveline.
The AMT Chevy Vega model kit was updated to a 1978 Monza S, and reissued in that form within the last few years making it a common-ish model of a rare car.
No Wankel in the kit but it still has the original aluminum engine, it was never updated to the Iron Duke.
Apparently the HJ Roadpacer was fitted with a luxury floor dipswitch 😉
Factually incorrect article. The Roadpacer was built in Hiroshima from CKD parts (and not supplied by Holden as a built up). The lack of performance and excessive fuel consumption is grossly exaggerated. A 2.5 tonne bus was fitted with the same engine.
Accounts differ. We found this version most credible. If you have written documentation we’d be happy to share it.