Coupe De Kill

A tuff-boostin' TD Gemini coupe that's set to take on the hard-edged monsters in the 10-second bracket!

Words by Michael Knowling, Pix by Julian Edgar

Click on pics to view larger images

Holden's venerable Gemini has always had a strong following. But no one could possibly love a good Gemini more than John Parisi of Melbourne. He's been a Gemi man for many years, and has bought and sold no less than eleven Geminis! Yep, you could say he's a total nutter for these little cars. But it's only been in the last three years that John's decided to really go to town - he just had to see how spectacular a Gemini could get....

In the first scene, John and a mate Richard (who's basically responsible for the whole mechanical makeover) grabbed an imported G180 Isuzu donk. As well as boasting a 200cc capacity increase over the standard motor, this beastie also possesses some pretty tough looking internals. It was the perfect cost-effective base for an absolute mega-grunter. Richard grabbed his spanners, stripped the motor, slipped in SPS forged pistons (delivering a compression ratio of near 8.0:1), shotpeened rods with new bolts, and a Crow timing chain. It was also treated to a full bottom-end balance. Upstairs, the stock 8-valve head's been cleaned up, fitted with bigger stainless exhaust valves, heavy duty springs, a copper gasket (together with O-rings) and a pretty wild Crow cam.

After the basic engine assembly, the guys looked long and hard at a custom turbocharging system. Richard then produced this work-of-art mandrel bent tubular exhaust manifold to mount a dirty big mutha of a T04 turbo. Teamed with a 42mm Garrett external wastegate (instead of a previously too-small 32mm 'gate), this thing spools to 15 psi on the street - and a full 30 psi on the drag strip. John likes to keep things safe and conservative on public roads... Initially, this induction system was completed with a simple Holley 650 four barrel carburettor that was mounted pre-turbo (ie in a draw-though configuration). The advantage of doing it this way was that they didn't have to modify the carb to suit boost. Its flow was also seen as a strong point.

With a cookin' motor begging to be driven, John searched for a solid year before coming up with a rust-free, one-owner '78 coupe - in completely stock condition. And for a measly 200 bucks, it was a ripper bargain! Before long, he'd set to work performing some odd panel repairs and preparations, before stripping the pretty body completely naked for all to see. What went on next is a colour that some people may have already picked the origins of - it's a Holden Barina colour, called Bocca yellow. It sure looks better on the Gemini than it does on a Barina though...

Complimenting this unique paint job is a set of classy 17-inch Simmons wheels surrounded by 235 and 215 40-series Avon rubber. The latter required modifications to the inside of the guards.

This exceptionally tidy looking Gemini is poised on a suspension system that's 100% standard - except for 90/10 front and 70/30 rear dampers. An upgrade in this area is on the cards though. And, despite the suspension being mostly stock, we're thankful to report that the brakes are significantly beefed up. John installed a Rod Hadfield upgrade kit that comprises HQ (5 stud) front discs and calipers, and a set of Q'y drums for the rear. And, considering the weight difference between a Gemini and a HQ Holden, this must be a monumental improvement over the standard anchors. Certainly, the stockie Gemini items would've turned to dust trying to slow down an engine like this!

The Celebration of a Coming Together...

In early Y2K, both the fully prep'd body and the turbocharged G180 were united. It was a coming together that must have pleased the Gods no end. However, the occasion also called for a few other tweaks around the engine bay - such as an aluminium radiator, twin thermo fans and an oil catch can. And - with a monster motor - then came the task of filling the trans tunnel. It was the General's own Trimatic that got the nod and, in its current modified and manually shifted form, it's performed very well. From here, a custom heavy-duty tailshaft is used to connect drive to a mini-spool Ford 9-inch diff that spins a 4.3:1 ratio. Also running along the undercarriage is a full 3-inch mandrel bent exhaust, which receives the remnants of the G180's fierce combustion process.

Needless to say, this lethal package went like the proverbial cut snake and some serious power was certainly being made - but there were a couple of hiccups (literally!). Apparently, the draw-through carby set-up was severely affected by changing temperatures and was a real pain in the arse to tune. Some people in the industry would say it couldn't be tuned properly at all... Both John and Richard knew that the only real solution would be to swap the suck-through Holley for the flexibility of a programmable ECU. Simply farting around with jetting and butterfly staging (and whatever else) was only going to consume endless amounts of time and yield second-rate results.

So, again, Richard (and another guy named John) got out the metal working equipment and set about constructing a custom intake manifold (with gently radius'd bends) and cylindrical plenum chamber. The chamber's "in" hole is through a large XF Falcon throttle butterfly.

Then - only a couple of weeks before our photo shoot - JPC finished installing and tuning a Microtech MT8 ECU and a brace of four Bosch 351 injectors (fed by a custom rail). A Holley Blue pick-up pump, custom surge tank and a 500hp Bosch main pump supply a steady stream of life-blood. Obviously, a return line also needed to run fuel from the rail back into the standard tank. The mighty usually G180 dines on Shell Optimax when John's driving on the street, but a more volatile concoction of Avgas or BP race fuel is the go for track visits. The ignition system, too, is controlled by the Microtech computer, which works in conjunction with a stock dizzy, single Bosch coil and one range cooler spark plugs.

The Outcome...

In its new-and-improved fuel injected form, John's Gemini has powered down the quarter mile test in a blinding 11.1 seconds at 119.8 mph! And there were even a couple of problems (such as sticking brake caliper!) at the time. Onto the chassis dyno, it can also now crank out just under 200kW on 30 psi. And that's p-l-en-t-y. "EFI really is the way to go," enthuses John - who's now got the straightline performance to out-barrel even a top Ferrari or Lambo. But things aren't stopping there for this slick Gem. You see, John's aim is to crack the 10s with the car as it is...

Maybe then this Gemini will be long-term a keeper!

Contacts:

JPC (Johnson's Performance Centre)
+61 3 9465 2244

A Grade Automatics
+61 3 9354 1088

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