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A Miata-Powered Ford Cortina?


Story and photos by Robert Bowen

Most of us who drive late-model iron often catch ourselves dreaming about a perfect vintage ride: something old but not ancient, reliable, good-looking, and fast enough for modern traffic. Of course it would have to be leak-free and light on required maintenance—a machine that allows more time for driving over wrenching.

That modern-engine-plus-vintage-car combination would seem to be the ideal way to enjoy an old car with the best of recent technology, but many such conversions are cobbled together or rough around the edges. It takes someone with attention to detail and the eye of an artist to engineer a truly clean swap.

Mazda USA Technical Specialist and old car nut Brett Stierli might be just that kind of person. He seems to have found the perfect combination of vintage tin and new heart in his Miata-powered Cortina.

Brett’s choice of engine is no surprise—Mazda issues his paychecks, and familiarity with the marque dictated his decision. But why Miata? Because that model has a very popular drivetrain for swapping into other rear-wheel-drive platforms. The engine has proved to be tough and reliable with a smooth-shifting transmission and enough power to be interesting.

“I always wanted to put a new motor into an old car,” Brett explains. “I have a Mazda background, so it was natural for me to look for a Mazda project. I started out with an engine from a wrecked 2001 Miata and looked for a car to do an engine/powertrain swap.”

Business Valuation

While a Ford Cortina was always Brett’s first choice, he tossed around ideas for a couple of other cars. “I also considered the Mazda RX-4 and Chevrolet Cosworth Vega,” he explains. “The RX-4 was ruled out because they are hard to find and because parts are just too hard to get. I found a Vega, but the engine compartment on those is weird so I struck that idea.”

His little Mk II Cortina is an unexpectedly rare choice in the U.S., but it looks cool and has a vast aftermarket in other countries. “Cortinas are hugely popular in the U.K. and Australia, more or less like Mustangs in the U.S.,” he says. “Plus, Ford and Mazda have been together for a while, so I didn’t feel too guilty about it.”

The donor car was easier to find than Brett had expected, as placing a single ad in a local classified paper did the trick. The ad was simple and to the point: “Wanted: Ford Cortina or Mazda RX-4, any condition.” Within a week Brett received a couple of calls, one of which led to this exceptionally clean, two-owner Mk II Cortina.

“As soon as I walked up and saw the car, I knew I would buy it,” he recalls. “It wasn’t rotten, and it had the original interior, original paint and everything—it even still had dealer license plates from a local Ford dealer. It had always been on the road, always a daily driver, which is why it stayed so nice. I paid $900 for it right then.”

Resource Transfer

“When I bought it I drove it as stock with the original wheels and everything for a couple of weeks, which was cool,” Brett recalls. “Then I stripped it down to the bare shell and brought it to my fabricator. I dropped everything off at his shop and said, ‘Make it fit.’”

Brett’s longtime acquaintance, fabricator Kerry McDonagh, engineered the body modifications and brackets needed to get the Miata engine into the Ford’s engine bay. Lucky for him, the Miata engine was not much larger than the Cortina’s original 1600cc Kent engine—the ghost of which is probably powering a Formula Ford racer somewhere.

“No firewall modifications had to be made,” Kerry says. “The transmission fit pretty well, too, because it was originally automatic—the only problem was a shifter hole that was 3 to 4 inches too far forward to be perfect.”

Kerry cut the shifter hole back about 3 inches and fabricated a plate to use the Mazda’s shift boot. He then turned his attention to the radiator core support and engine mounts.

“The core support had to be moved forward because the engine is longer, but even with it moved I had to use a Spal radiator fan because there wasn’t enough clearance between the engine and the radiator for the stock Miata fans.”

To alleviate any potential cooling problems, the radiator was sourced from a turbocharged Mazdaspeed Miata. The Mazdaspeed cars got a larger radiator than the standard-issue Miatas.

“Other than the core support and the floor modifications, the engine required very little fabrication to get it in there,” the car owner explains. “Kerry mounted it with modified urethane sway bar mounts that later turned out to be too harsh. There was nothing wrong with the mounting, but it made the car pretty noisy and bumpy. Later I took it back to fab new mounts that used the stock Miata rubber insulators.”

While Kerry had the Cortina at his shop, he also built some of the other distinctive parts, including the seat mounts, roll bar, aluminum rear bulkhead, sump guard and light bar.

For the rest of the build, Brett tried to use as many Mazda parts as possible in order to keep the project reliable and inexpensive. A Protegé5 donated its pedal box, for example, while the wiper motor came from a Mazda Tribute.

Even though Brett threw several Mazda parts into the mix, he wanted to keep the car distinctively Ford. He machined off the Mazda lettering from the valve cover and added a Ford badge sourced from a Probe.

“I didn’t want the motor to have a Mazda identity,” he explains. “Sometimes people have no idea what the motor is, others figure it out.”

Merger Control

Once the engine was in place, Brett started the tedious task of getting it wired and plumbed for fuel. The wiring harness for the engine and dash were made from a stock Miata piece for ease of diagnosis and repair.

“I cut open the stock Miata harness and rerouted and spliced all the wires to fit this car,” Brett explains. “The only Cortina wiring is the headlight harness, and the rear wiring harness and turn signals. Everything else is stock Miata wiring—a Miata wiring diagram could be used to diagnose it.”

The gauges presented an interesting problem. The donor Miata used electrical gauges, so it had no speedometer drive gear, and the engine control system was integrated with the instrument panel. To overcome this hurdle, Brett had to reengineer the Miata gauges.

“I pulled apart the Miata gauges and put the internals, faces and needles into the Cortina housings,” he explains. “I traced the factory instrument panel circuit board and basically recreated it with hard wiring in the gauge cups. The glass, lens and bezel are still Cortina. It works well because the Miata has a retro-themed gauge look.” The speedometer and tachometer work just as designed, helped by the fact that the Miata and the Cortina share the same rear axle ratio.

The Miata’s fuel system presented another challenge. Like many late-model cars, the 2001 Miata uses a returnless fuel system—the regulator is integrated with the fuel pump and the filter is fitted inside the fuel tank. Since Brett planned to use a fuel cell, this meant that the stock in-tank fuel pump module wouldn’t work. The most logical place to put the cell was in the trunk, but that would mean reducing the already minimal trunk space, and a view of some ugly plumbing.

To solve this problem, Brett cut off the top half of the stock Cortina fuel tank and mounted an external pump, filter and regulator in the space normally taken by the stock tank.

Of course the pump was taken from yet another Mazda. “The pump is from an ’85 Mazda RX-7 GSL-SE, which is the only external Mazda fuel injection pump,” Brett explains. “It works with the stock Miata returnless fuel system. I could have used an aftermarket pump, but they’re expensive and the RX-7 pump is a very good one and very reliable.”

The engine surprisingly maintains the original Miata catalytic converter and other smog equipment with the exception of the charcoal canister. “The car is too old for smog checks so it really doesn’t matter, but I wanted to keep the engine as complete as I could,” he says.

Once the engine was in place and the wiring sorted, Brett thought he was nearly done with the hard part of the swap. Unfortunately, the stock antitheft system turned out to be a bigger hassle than anticipated. In fact, according to Brett it was the most challenging aspect of the project.

“The first time I turned the key it would crank and crank but not start,” he recalls. “It was the immobilizer. I had a PCM from one car, and the steering column from another, which didn’t match. I had to basically reprogram the ECU with a blank immobilizer code and add an immobilizer box that matched the steering column and keys I had.”

Once the immobilizer problem was overcome, the car started right up and ran perfectly. Between the original steel wheels and faded red paint, the car was a real sleeper on the street.

“It looked like a beater but drove like a new car,” Brett says. “I drove it up the 5 freeway in the fast lane, up the Grapevine in fifth gear at 4500 rpm, surprising people as I passed them.”

Window Dressing

With the car running perfectly and the mechanical work behind him, Brett began the long task of cosmetically restoring the Cortina. Luckily the car was straight and not rusty, so Brett tackled this part of the work rather than contracting it out.

“After I finished the car, I totally disassembled it again and did all the paint and body work in my garage,” Brett says. The paint is the stock color, matched to an unfaded sample found on the car.

However, the car needed more than fresh paint. It needed a theme. The car’s look is an amalgamation of different racing Cortinas, most of which have roots in rally competition. The idea of using the square number panels on the doors, for example, came from a picture of a Mk II Cortina that competed in the London to Sydney Rally. The number 70 represents both the year the car was made, 1970, and the year Brett was born.

The stripes are not from a classic Cortina example, but they are from a domestic influence. “I added the three stripes to make it look like the Mustang GT paint scheme,” Brett continues.

All of the graphics, including the English Ford Line emblems on the rear quarter panels, were laid out and cut from vinyl by a local shop. The vintage race stickers came from eBay, also the source of the vintage Cibié spotlights and Lucas headlamps. The alloy fuel door cover and rear light were more nods to vintage rally. “I saw some vintage rally cars with single rear-facing spotlights, so I added one and wired it as a back-up light.”

Future Earnings

About two and a half years after first picking up the Cortina, Brett rolled it out of the garage sporting new paint work and a gutted interior. The project was as good as he had hoped—the combination of classic looks and modern power is a strong one. The car has been dead reliable since he finished it, requiring only minimal maintenance.

While he also owns a restored ’66 Mustang convertible, Brett prefers driving the Cortina. “I drive it pretty much every weekend—mechanically it is a late-model Miata, and it’s just like driving around in a new car. Pull off the cover, turn the key and it’s ready to go.”

If there’s a problem, it’s the fact that most people don’t know what it is. Some mistake it for the much more common Datsun 510 thanks to its overall shape and the air vents found at the base of the C-pillars.

As for future plans, Brett hopes to do something about the tired suspension, including a possible swap to urethane bushings. “The suspension and brakes are all stock Cortina GT spec, which is pretty good, but it could use tightening up,” he explains. Another item on his list involves returning the interior to something more resembling stock. “I would also like to have a headliner and carpet, but that means pulling out all the glass, which means all new rubber seals.”

No matter what other changes he makes to the car, it’s hard to imagine that it could get any better. It’s a vintage car with modern reliability and custom-car levels of fit-and-finish. Few rides can one-up that kind of combination.

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Comments

View comments on the GRM forums
wspohn
wspohn Dork
11/27/17 11:52 a.m.

Nicely done project.

Needn't have looked that far for an engine candidate, though.  Up here in Canada, unlike the US, we got the Mk 3 Cortina - the next body style along, and it came with the SOHC 2.0 engine also used in the Pinto, that had far more scope for development that the old pushrods.

Have to agree that a modern engine with modern management is several steps beyond that, though.

RossD
RossD MegaDork
11/27/17 12:11 p.m.

That's a pretty car with a nicely executed swap. Just pretty all the way around. yes

Robbie
Robbie PowerDork
11/27/17 12:31 p.m.

Awesome. That is basically exactly what I plan to do with my miata 1.6 motor and my MGB-GT I have sitting in my garage! Hopefully mine will turn out almost as nice.

Keith Tanner
Keith Tanner MegaDork
11/27/17 12:32 p.m.

MGBs and Miata engines are a perfect match.

I dig this Cortina as well - and I could have told him he'd have trouble what that immobilizer laugh

alfadriver
alfadriver MegaDork
11/27/17 1:15 p.m.

That is really, really well done.

The only other option I would have considered would have been a Duratec/MZR 2.0 or 2.3l.

Very, very cool.

Keith Tanner
Keith Tanner MegaDork
11/27/17 1:23 p.m.

Funny, I once suggested buying an engineless Alfa GTV and putting a Miata drivetrain in it and was told it was a terrible, awful idea.

bentwrench
bentwrench Dork
11/27/17 1:26 p.m.

I'll take the Cortina with a Duratec 2.4L (or equivalent) please.

alfadriver
alfadriver MegaDork
11/27/17 1:37 p.m.
Keith Tanner said:

Funny, I once suggested buying an engineless Alfa GTV and putting a Miata drivetrain in it and was told it was a terrible, awful idea.

If there was a modern Alfa equivalent engine, that would be fine. Replacing a Ford engine with a Ford engine (the BP was in a few Ford cars) seems fine.

Or if you find an $1000 GTV, you can do whatever you want.  Last time I saw one of those was 15 years ago.

Keith Tanner
Keith Tanner MegaDork
11/27/17 1:48 p.m.

So a Chevy engine in an MG is okay, but a Mazda engine in an Alfa is not? cheeky

alfadriver
alfadriver MegaDork
11/27/17 2:26 p.m.
Keith Tanner said:

So a Chevy engine in an MG is okay, but a Mazda engine in an Alfa is not? cheeky

sue me for pointing out that an Alfa GTV is worth more than a Cortina or MG.  If you want to take value out, it's your money.

Still- I'd personally lean toward at least having an engine from that company.

dean1484
dean1484 MegaDork
11/27/17 2:33 p.m.

Better to re-power a car with any engine than let it sit and eventually get crushed.  I got tired of people telling me that the world would end if I used anything but a Porsche motor in my Porsche.   I quickly figured out I did not fit in with those Porsche people.  If I had an Alpha I am betting that there would be an angry mob of Alpha owners at me door with pitchforks.

I will say that a GTV6 really needs a V6.  Putting a 4 in it Makes it a "GTV6 - 2"  cheeky  

alfadriver
alfadriver MegaDork
11/27/17 2:44 p.m.

In reply to dean1484 :

Calling them Alpha's would bring out enough pitch forks.

But if you want to take a car and gut it's value, it's your option.

A long time ago, there was a guy who was putting an S2000 engine into a GTV.  Had to cut a lot out of the car just to make it fit.  Ignoring the really badly done interior, taking a car that's worth $20k, spending $15k to modify it, and resulting in a car with maybe $10k does not seem like a good idea to me.  Especially when there really isn't a shortage of Alfa donor motors that drop right in (Spiders rust nicely, but the engines and trans's survive rather nicely being aluminum.  Or you can get a late 164 TS motor that's more modern, and that does not take out that much value, too.  

This car was bought for $1000, and since it's not a Lotus, it's not really worth much to start with.  So it's not as if the owner was throwing money out the window.  Nor was it cut up a lot to make the engine fit (I suspect).  AND the installation was really well done.

Oh, and we are talking the Bertone GT (Jr, GTV, etc) from '65-74 not the GTV6 from the 80's.  The GTV's are worth quite a bit more than GTV6's.

Keith Tanner
Keith Tanner MegaDork
11/27/17 3:03 p.m.

Ah, at the time the GTV was $7k if memory serves. Had no drivetrain but a nice body. It's not an option anymore, but I remember getting quite a bit of "no, not okay" when I floated the concept.

Subaru engines in the $15k VW buses seem to be well accepted. As do repowers of Land Rovers. I swear that just about every internal combustion engine has ended up in a Series Rover at some point.

trucke
trucke SuperDork
11/27/17 3:47 p.m.

That is gorgeous!  Great build!

alfadriver
alfadriver MegaDork
11/27/17 5:00 p.m.
Keith Tanner said:

Ah, at the time the GTV was $7k if memory serves. Had no drivetrain but a nice body. It's not an option anymore, but I remember getting quite a bit of "no, not okay" when I floated the concept.

Subaru engines in the $15k VW buses seem to be well accepted. As do repowers of Land Rovers. I swear that just about every internal combustion engine has ended up in a Series Rover at some point.

Start with a $7k GTV, put $2k of work into putting a new engine in it, and it will be worth $7k.  Less if you had to cut the chassis badly to make the engine go in.  Put an Alfa motor in it, and it will be worth a lot more money.   Even if the donor was a '79 Spider.  

Again, it's your money, so if you want to do that, you are welcome to.  But the point of it being "not ok" is very financial.  

It would be a lot better financially to do that with a Spider than a GTV.

Would Singer cars be worth as much if he used a Subaru flat 6?  I doubt it.

Keith Tanner
Keith Tanner MegaDork
11/27/17 5:11 p.m.

I don't build cars to resell them. Not me personally, anyhow. If a Miata-powered GTV is more fun and easier to live with than an Alfa-powered GTV, then it's a better car. Never having driven both, that's kind of a theoretical exercise.

Spiders hold absolutely no interest to me, so a Spider with a Miata engine is just a crappier version of a Miata. An MG with a Miata engine is an idealized MG laugh Don't ask me to explain.

jimbbski
jimbbski Dork
11/27/17 6:03 p.m.

If you want modern and can afford the higher cost I'd go Ford 1.6 Ecoboost.

alfadriver
alfadriver MegaDork
11/27/17 6:29 p.m.

In reply to Keith Tanner :

Not sure how I got to be the focus, since this seems like a great swap.

But I will finish with this- a BP swap for this car would be a considerable improvement.  Just like an MG.  But it's certainly not for an Alfa.  And it's not as if I've not driven both, a lot.  It would be a whole lot cheaper and easier improving the Alfa 2.0l and resulting in a more powerful motor than swapping any BP in an Alfa.  Not to say a BP is a not a great motor- it is.  But the assumption that the Alfa 2.0l is somehow the same as a basic 1.6l Kent motor or the MGB motor, well...  

Then again, I'm a real oddball, here- I'd much rather race and autocross my Alfa than a Miata.  I autocrossed my '95 once.  And my GTV hundreds of times.  Never did a lap in my +200k miles in a Miata, spent hours in my Miata.  I'm quite certain that a Miata motor would not make the Alfa any better- other than it running a little better and it having better emissions.

codrus
codrus UltraDork
11/27/17 7:08 p.m.
Keith Tanner said:

Subaru engines in the $15k VW buses seem to be well accepted. As do repowers of Land Rovers. I swear that just about every internal combustion engine has ended up in a Series Rover at some point.

 

No pistons allowed in an RX-7, though. :)

Daylan C
Daylan C SuperDork
11/27/17 7:40 p.m.

In reply to codrus :

So keep my Honda powered 1st gen RX7 thoughts to myself? 

OHSCrifle
OHSCrifle Dork
11/27/17 8:05 p.m.
alfadriver said:

In reply to Keith Tanner :

Not sure how I got to be the focus...

 

I don't think you are, tbh... 

JoeTR6
JoeTR6 HalfDork
11/28/17 6:06 a.m.

I really like this build.  It's similar to the '73 Capri/Ford Ecoboost I want to do.

Flynlow
Flynlow HalfDork
11/28/17 6:36 p.m.

Wasn't this car featured in GRM a few years ago?  I thought I remembered reading about it a while back...

Keith Tanner
Keith Tanner MegaDork
11/28/17 6:53 p.m.

This is a "reprint" of an article from 2008.

pres589
pres589 PowerDork
11/28/17 7:12 p.m.

What about a street ported 13B in an Alfa GTV? 

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