Resurrection: The Pikes Peak 20B 4WD RX-7

Exactly four years, 10 months and 24 days previous to this story, Speedhunters poked its nose into a shed in the rural outskirts north of Auckland, New Zealand. Modest in stature and tucked away from prying eyes, inside the resurrection of a modern legend was taking place.

That legend, an ex-Rod Millen, ex-RE Amemiya, 4WD and 20B-powered FC3S Mazda RX-7 that originally earned its stripes throwing stones up the curves of Pikes Peak.

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You can read all about the history of the car and how it ended up in New Zealand in Brad’s 2012 post, but for now we’ll focus on the current status of the RX-7, as seen cutting laps at Rotary REunion this past summer.

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Being endowed with this insatiable thirst for all things race car, especially for those with provenance, it was always going to be a given the RX-7 would end up in front of my lens in some capacity. After a quick chat to the man responsible for its ground up restoration and further enhancement, Grant Munro, we trundled down the end of Bruce McLaren Motorsport Park’s pitlane for a few shots and a chat.

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See all of those panels? They may look OEM – the aesthetic of course dictated by the Open Class rules that Millen and the RX-7 were required to meet at Pikes Peak – but they’re entirely fibreglass, bolted to what’s by-and-large a space-frame chromoly chassis. Grant explained the rules allowed something like 95 percent of the chassis to be tube, and in this case the only factory sheetmetal present on the FC is the A-pillars and some of the firewall. Some of it.

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While the original livery was cast aside not long after Millen on sold the RX-7, when the car came into Grant’s possession, the scruffy panel work was only ever going to receive one livery. Aside from a few small sponsor decals, he has reinstated the iconic Mazda USA colour scheme as employed by Millen across an array of his rally and hillclimb machinery, from SA22 RX-7s through to the BFMR-chassis Group A 323s.

The resultant aesthetic is pretty much bang on. Amongst the metallics, candies and ‘West Auckland harlequin’ (that’s a colloquialism for matte black in Kiwi speak) tones of REunion’s assembled throng of rotary-toting cars, the 1980s honesty of the livery stands out. It’s everything that’s great about an era before the age of digital design reared its complex head.

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While all four of the RX-7’s fibreglass arches house a set of pristine three-piece BBS LMs in lieu of the original, unobtainable magnesium Panasport wheels, the timeless split-spoke style looks perfectly at home, especially when shod with the semi-slicks more in keeping with the kind of use Grant intends for the car these days.

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Sooner or later though, the eyes can’t avoid lingering on those two flame-spitting pipes exiting the passenger door. Those pipes, and their neatly-crafted stainless steel heat shield, offer up an invitation to check out what’s going on beneath the skin. And trust me, this is where things get really interesting.

This Ain’t OEM
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As alluded to earlier, while the exterior of the RX-7 retains a factory silhouette, beneath the lightweight panels things are about as far removed from stock as you’d likely get. As soon as Grant lifts off the fibreglass hood (which the sharp-eyed reader will note belongs to a non-turbo FC), three rotors of Mazdas finest lie beneath a jungle gym, and disappear beyond the scuttle panel.

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Grant’s summation of “some of the firewall” is fairly spot on. Around a third of it remains, conveniently in front of the driver’s feet. But let’s talk about that 20B.

In its initial incarnation, Millen ran the FC with a 13B turbo providing the necessary motivation. A few years later, with the bit between his teeth and a goal of taking out the Open Class record, he returned with an extra rotor. The then new 20B represented the pinnacle of consumer rotary engine tech and the tilt at Pikes Peak for 1991 saw the engine remain essentially stock, save for a single turbo conversion with an associated tune on race fuel yielding a useful 500hp or thereabouts.

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Under the distinctive 3-ROTOR inlet manifold, however, Grant’s drawn on his extensive knowledge to build a better 20B. Being in the business of piecing together rotaries, Grant has ported the 20B to a ‘Stage 2′ level, added unbreakable 2mm apex seals as well as treating the engine to improved oil galleries and a thorough balancing of the rotating assembly.

As well as the beefed-up short block, the RX-7 now runs a GReddy T88-33D turbo, a remnant from its post-PPIHC days as an RE Amemiya show/demo car. Grant reckons the turbo was essentially brand new when the restoration began, and with updates in the form of a Turbosmart 60mm wastegate and TiAL blow-off valve, the 20B is good for 600hp. Add that to the 800kg dry weight of the car, and it’s a recipe for a hell of a good time.

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While it’s tough to actually see the intricacies of the 4WD system, it’s worth a brief explanation. The FC3S wasn’t Millen’s first 4WD RX-7 effort, and lessons learned on championship-winning first-gen RX-7s were enacted on the FC. Like the earlier cars, the FC3S uses a modified Alfa Romeo front diff unit, chosen for its compact nature. Sending drive to the rears is a Mazdaspeed LSD-equipped FC3S diff, while in the middle there’s a Weismann 5-speed dogbox paired to a transfer case from the same manufacturer. The torque is split 50/50; no fancy active diffs or electronics are at play.

Suspension remains as per the original arrangement. When Brad left off from his mid-build visit, Grant was in the process of refurbishing the Bilstein remote reservoir coilovers. They now hang from the tube structure at both the front and rear of the car, and peering up from beneath the rear bumper presents a pretty graphic vista of just how little FC3S is left in this thing.

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Like any good single-minded speed creation, the interior is spartan. The bare necessities remain: a rudimentary dashboard, period steering wheel and simplistic shifter. Floor and tunnel panels are all hand-formed alloy.

Electronics have also been brought into the 21st century. Grant’s elected to run Haltech’s Platinum Sport 2000 ECU, a choice dictated no doubt by leaps and bounds in engine management technology over the past 30 years. Keeping an eye on the vital functions have never been simpler thanks to the accompanying Haltech display perched atop the alloy dash.

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There is one other major change to the interior: the addition of a passenger seat. Grant thinks it’d be a bit unfair to keep the experience of such a raw piece of motorsport history all to himself, and the installation of a fixed-back bucket with a harness means that unsuspecting victims can be subjected to a triple-rotor thrill.

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I wasn’t lucky enough to strap myself into the seat this time around, or perhaps I just wasn’t organised enough, due to scurrying around like a madman pointing the camera at all things rotary during that weekend. But like the promise after Speedhunters’ last visited this iconic RX-7, we will be back. Except this time, we’ll be along for the ride.

Richard Opie
Instagram: snoozinrichy



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Please tell me there is some sort of video of this thing. I want fire breathing rotor goodness


Here you go. I saw this pop up on my facebook just 2 weeks ago.


I'm loving all these rotary posts!


I reckon I could contribute a years worth of quality Kiwi rotary content...


If you go back and read the initial post it makes this one even more special. What an epic speedhunting story. Thanks for keeping your word!
I wonder if Rob Dahm knows about this :)


I'm really glad someone went back and read the original - it gives a great context to this story, without me having to regurgitate all that Brad previously said about the car.


"Been there, done that" too :D


Ahhh Ashley Forest, good times. Different car but I'm sure you know that!


Whoops nah i didn't know. I remember seeing this video a while ago and just assumed it was the same car.


Yeah that one's a 13B PP naturally aspirated car, still super, duper rad!


Thanks for adding some info on the gearbox/drivetrain setup. This part is often forgotten in articles on this site.


I'm a bit of a tech nerd, so always attempt to give some detail as to what makes things tick! Glad you liked it, keep an eye out for a few more little Kiwi features moving forward.

Malcolm Craig

Now this is exactly the kind of article I look forward to: a car with history, exciting technical specs, and a great story. More like this please!


Mazda should have built this as an SP production model!


The lack of creature comforts might have been a concern for some!

Jay Soh Tsu Chung

With the exhaust arrangement like that, where does one place their feet when they are strapped in for a ride?


I'll be able to tell you soon enough, where the feet go - there is a big heatshield box in the footwell, but I'm still excited to find out.


You can't beat that livery design. It's so overwhelmingly 80s. I love it. And to see a full-on tube-chassis car without crazy aero is just the coolest. I actually didn't know about this car until today, but the care that's been given to it now coupled with the car's past make it one of my favorite features of the year.


I was hoping the end of the article would go something like "...and you can expect to see these guys at the top of Pikes Peak later this year."


Imagine that! Grant's quite literally a one-man operation just tinkering with some mad rotaries however!


My dad bought the original "millen miata" from rod back in the early 90s and I showed him this article. He said that car was out front when he picked it up. Motorsports history is so cool!


Rad, any pics? Sounds like a sweet wee car. I don't know much about the Millen Miata... Google shows me it was yellow?


Lovely sharp vibrant photos of an awesome car. Keep up the good work.


Richard, Do you know what model Alfa the front diff is from?


Sorry Scott, I'm not totally sure of this one. From looking at it, it looks very much like a 105-series era (it is pre-Alfetta, as these used transaxle) with the output shafts modified to accept a 6-bolt CV joint. The car uses early Mazda 626 driveshafts and CV's in the front if I remember right. But yeah... you're lucky I'm an Alfa Romeo nerd!


I am loving all the rotary love this month! This makes me excited for the possibility of an update on Rob Dahms AWD RX7!


Very cool


Great article. I took the effort and read the old article too. What a story :o If car would talk....


What a story :o I have read the old article too. Epic! Thank you for great story man,you did a great job.


Now this is true Speedhunting


Loved reading this article, its nice to see the continuation for the previous article.

P/S: You guys should do more retrospective posts, they are really interesting!


Munro? Is this guy related to the legendary Burt Munro?