Owen Coster’s brand of car modification is rare these days. While it’s
becoming common to splurge wads of cash on workshop modifications - and then say
"you" did it! - Owen’s approach is refreshingly different. When he needed an
intake manifold for his Holden he machined it up. When he decided to go
injection he bloody well did the hard yards, rewired the entire car and trod
where no one has ventured before.
Owen is a qualified fitter and turner and he certainly isn’t afraid of
getting his hands dirty. And that’s just as well – you can’t do up a 1966 HR
Holden without gettin’ slightly grubby!
Owen says he never planned to build an HR Holden. He originally wanted to
revive an EH Holden but high prices meant he had to look elsewhere. It was a
friend who spotted this HR for sale on the side of the road and gave Owen the
The car was exactly what Owen was after – the previous owner had spent 18
months massaging the paint and panels but much of the driveline, suspension and
brakes were pretty tired. After a bit of haggling, Owen came away the proud
owner of a tru-blu piece of motoring history. In the next few months, the
existing 186ci (3050cc) engine was treated to a hot cam, X2 intake manifold and
twin Stromberg carbs. With a four-speed M20 manual ‘box, the car managed a 17.7
second quarter mile – pretty much what you’d expect given a tired engine.
And then came the day when Owen decided to re-power.
Owen called on another mate who had previously rebuilt a 186 with ACL 9.8:1
flat-top pistons, a Romac harmonic balancer, lightened flywheel, balanced rods
and a balanced steel crank. The engine had also been bored 60 thou bringing
total displacement to 192ci (3149cc). The entire bottom-end was sitting in a
shed gathering dust – so Owen offered some dollars and came away with a bargain.
Next, he managed to source a Yella Terra head and proceeded to have it rebuilt
with upgrade valves, springs and guides. An aftermarket cam was also fitted. At
this time, Owen intended to run the new engine with a tried-and-proven Holley
But then things veered off the beaten track.
Another mate (who was performing a V8 conversion) offered a VK Commodore
electronic fuel injection system – computer, airflow meter, injectors and
throttle body assembly. By this time, Owen had grown tired of carburettor
adjustment and recognised the many advantages of going EFI – and it was hard to
ignore that the VK system was being offered for next to nothing!
Installing the new management wasn’t so simple. Owen saw that the standard 40
year old wiring was a bit dubious so, together with his father, he rewired the
entire car. The rewire includes hazard lights (which were never factory fitted),
courtesy light switches for the back doors, a security system and a conversion
from glass to blade-type fuses. Halogen headlights also replace the original
sealed beam candles. And the EFI integration? Well, that was made a whole lot
easier using a VK Commodore wiring manual. A Silicon Chip Digital Fuel Adjuster
(DFA) was also wired in to give the tuning flexibility that was thought
necessary with the big cam.
The hardware side of the EFI system also required a lot of time and effort. A
friend (Steve) designed a suitable intake manifold, folded the metal and
performed the necessary welding while Owen did the machining. Unfortunately, the
custom manifold didn’t have adequate clearance against the left inner guard so
Owen had to shorten the runners and angle the throttle body. Now it fits!
Owen employed a length of extruded stainless steel to fabricate the injector
rail that connects to the standard VK Commodore injectors. There’s also an
electric in-tank pick-up pump that feeds a surge tank and a Holden VL pump
supplying fuel to the engine. High-pressure EFI hoses (including a return line)
and a Malpassi adjustable regulator are also used.
The exhaust manifold was yet another cost-effective second-hand purchase -
you don’t turn down a set of aftermarket headers for 20 bucks, do you? Owen has
added heat wrap to the headers and, from the collector, he and a mate have
installed a 2 ¼ inch mandrel exhaust – this was done on the ground at home, but
Owen says he’d never do it again without a hoist...
Intake air flows easily thanks to an aftermarket pod filter which is mounted
on the end of a pipe constructed from sections of stainless steel mandrel bends.
This pipe connects directly to the VK airflow meter and a silicon elbow guides
air into the mouth of the standard VK throttle body.
Also fitted to the air intake is a Morey’s Power Booster kit. The Power
Booster automatically injects a lead substitute chemical into the engine, which
eliminates the need to squirt chemicals into the tank at every fuel stop. The
kit relies on engine vacuum to draw the chemical into the engine (downstream of
the throttle) and the rate of flow is adjusted to suit using a variable valve.
Further investigation in the engine bay reveals a three-core radiator and 16
inch thermo fan, a custom valve cover and radiator header tank, fresh paint (to
match the body) and the absence of a battery (which now lives in the boot).
For the driveline, Owen opted for a heavy-duty clutch and pressure plate
combo (supplied by Direct Clutch) and he’s installed a hydraulic actuation
system. A five-speed Toyota Celica gearbox was sourced from a friend and has
been mated to the Holden six using some custom bell housing modifications. A
custom tailshaft then channels drive to a shortened VN Commodore diff. The diff
was purchased as a kit and is welded to original HR mounts.
And then came the moment of truth - firing ‘er up on the
With the engine running on C-N-J’s Dyno Dynamics chassis dyno it became
obvious there was a problem with cylinder-to-cylinder fuel distribution – and no
amount of management tweaking could fix it. The problem turned out to be the
combination of the old-school 9 port cylinder head (which uses three inlet
ports) with the six injector fuel system. But no stress. Owen went away,
fabricated some metal dividers for the inlet ports and returned to the dyno.
Fuel distribution was much improved and the car managed to generate 110hp (82kW)
at the wheels together with good driveability. It turns out that the standard
Holden management system copes well with the upgrade cam and other mods – so
there was no need to make airflow meter signal adjustments using the DFA unit.
Owen admits the current cylinder head set-up is a bit of a mutation – it would
be better to use a late-model factory 12 port head, but the current arrangement
seems to work okay.
And don’t think for a moment that Owen has neglected the steering, suspension
Owen tracked down a company selling a rack and pinion front-end kit
comprising an exchange front cross-member, new ball joints and a UC Holden
Torana rack. This was slipped into the HR for a dramatic improvement in steering
feel and response.
The suspension has been enhanced with a Fulcrum rear swaybar (the HR never
came with a rear swaybar from factory), a beefier front swaybar, Koni adjustable
dampers, King front springs and modified rear leafs. Nothing over the top – just
good, cost-effective upgrades.
The brakes are upgraded using a remote mounted VH40 booster with a standard
HR master cylinder pushing HT Holden two-pot front callipers. The rear brakes
are the original discs that came attached to the Commodore diff. Owen says the
rear brakes would lock when this set-up was initially installed so he added a HQ
Holden proportioning valve. Problem fixed.
As we said, Owen set out to buy a car in need of a driveline revival – he’s
not really into paint and panel work. For this reason, the HR’s appearance has
been left as-purchased. The only changes are widened 14 inch steel wheels which
enable fitment of beefy tyres.
A friend of Owen – Troy Cowen – can be credited for the interior revamp. All
trims have now been covered in velour and a Pioneer CD system has been added.
There are also AutoMeter gauges for rpm, oil and water temperature and a Silicon
Chip air-fuel ratio display (Owen has added a threaded bung in the front section
of exhaust along with a Holden 02 sensor).
Owen says the car was built to be driven – it was never intended as an
all-out speed machine. With predicted 15 or 16 second quarter mile performance,
Owen will never feel what it’s like to whip a Subaru WRX - but that’s not the
point. Instead, every time he fires ‘er into life he can enjoy the satisfaction
from all the time and effort he’s invested.
And, sadly, that’s a feeling that fewer and fewer car enthusiasts are
C-N-J Motorsport +617 3290 3966
Owen would also like to thank Steve, Troy, Kelvin, his father and everyone
who has helped with the project.
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