In Part One of this series we looked at the differences in engines
used from the EA to AU Falcon. Jim and Brendan Mock from J.M.M. (Jim Mock
Motorsport) suggested the best platforms for tuning are the EF and EL Falcon as
well as the Tickford XR6. However, since all of the good bits are
interchangeable, it doesn’t matter too much if you’re starting with a different
Now let’s look at approaches to modification...
Exhaust and Headers
Jim Mock says the best place to start modification on a Falcon six is the
"The standard exhaust system on the Falcon ranges between about 1¾ to 2
inches diameter for most of its length," says Jim. The XR6 exhaust system flows
better than a normal Falcon exhaust but it should still be the first area of
J.M.M. offers a number of off-the-shelf Falcon upgrades (which we’ll come to)
and all use a collector-back 2½ inch mandrel bent pipe. Jim suggests there’s no
need to go bigger than 2½ inch for a street/strip application.
"On a car making 170kW at the wheels our full-length exhaust causes only a
2kW restriction compared to having no exhaust at all," says Jim. Depending on
the components used, a cat-back system generally gives about 8 or 10kW at the
Note that the Falcon is also very sensitive to muffler selection - resonances
and excessive noise are common in custom exhaust fabrications. J.M.M.’s exhaust
systems are developed to avoid this.
And what about the exhaust manifold, you ask?
"When doing an exhaust upgrade you should replace the factory exhaust
manifold at the same time," says Jim. "The standard 2-piece manifold is pretty
basic and a good set of scavenging headers will make a tremendous
"We recently did a DEV 1 upgrade (comprising an exhaust, headers, spark plugs
and a retune) on an EF Futura and power went from 95 to 133kW at the wheels on
our Dyno Dynamics dyno. But that was exceptional – most cars make about
Once the exhaust system has been upgraded, the air intake is probably the
next modification on most people’s list.
"The standard intake is not very restrictive near the factory power level but
it’s an easy and cost-effective area to modify," says Jim. J.M.M.’s kits involve
converting to a large pod filter mounted inside the factory airbox. We’re told
that a drop-in aftermarket panel filter is unlikely to increase power.
Interestingly, Ford also increased the length of the bell-mouthed snout
inside the airbox lid of late model Falcons. This helps reduce induction noise
but, since the diameter of the snout tapers along its length, there’s more
restriction than earlier ‘short snout’ lids.
EB era air boxes are quite different to those on later models. Induction air
enters via the top of the airbox and Brendan Mock says you’ll get a guaranteed
power increase by removing the lid. The only downside is engine bay heat.
Contrary to popular opinion, J.M.M. says the EF Falcon’s divided passage
induction pipe between the airbox and throttle gives more power than the larger,
single-bore pipe used on the EL and AU. A fabricated 3 inch mandrel pipe is
necessary only for engines making more than 140kW at the rear wheels. Gains also
depend on the type of headers and exhaust system used.
The factory throttle body – which remained the same across from EA to AU –
doesn’t cause enough restriction to justify modification.
The non-variable intake manifold fitted to the MPFI EA to ED Falcon is
decent, but the dual-stage manifold introduced in the EF is a quantum leap.
If you own a pre-EF Falcon, the dual-stage intake manifold will bolt onto the
head along with a few other incidental changes. The pre-throttle intake set-up
must also be revised. The biggest issue is obtaining the appropriate ECU that’s
mapped to suit the new manifold and has an output to control the switch-over
Jim says you need an EL Falcon computer because it’s the only model combining
the dual-stage manifold with a distributor-type ignition – the EF and AU
computers are designed to run a coil-pack ignition system. We’re told the new
computer is a straight plug-in but there is a small amount of wiring work
And are there any gains in altering the manifold’s change-over point? No.
Ford got this spot-on with a switch-over point at around 3800 rpm.
Brendan Mock says the dual-stage intake manifold is good for more than 170kW
at the wheels before it should be ported. "There’s a lot of turbulence inside
the manifold that can be heard when it’s on a flow bench," he says. "Once it has
been ported you can hardly hear anything – airflow is much smoother."
Once you’ve done the easy bolt-ons your next move should be a new camshaft.
This applies even if you have a XR6, which already has a more aggressive cam
than the everyday Falcon.
Jim says the standard ECU (which uses a MAP sensor) doesn’t like being used
with long duration cam profiles. "For the best result you need the greatest area
under lift that physics allow," he says.
A more aggressive camshaft will improve high rpm breathing but the effective
rev range is limited by the flow limit of the SOHC head. "The EF Falcon’s 5700
rpm limiter corresponds to where the head flow drops off," says Jim.
Porting helps this situation but, really, the short-revving nature of the
engine cannot be overcome. Not with the SOHC head, anyway...
Depending on the specs of the camshaft, it’s likely that a firmer set of
valve springs will be required to avoid high rpm valve bounce.
Note that the XR6 camshaft can be slotted into a conventional Falcon engine.
And, although it’s claimed the XR6 engine uses firmer valve springs, J.M.M. says
there’s no measurable difference in spring tension.
Don’t bother trying to alter the cam timing while retaining the factory camshaft – you
won’t pick up any more power.
As a generalisation, the flow capacity of the Ford cylinder head gradually
improved with each model. The exceptions to this are the ED (which appears to
use the same head as the EBII) and the AU (which use relatively small
Jim says the EA head should be avoided - "there are weaknesses in the
casting, design faults and flow problems." The EB was slightly improved and the
EBII was better again.
The EF/EL head uses nice large ports and runners and improved combustion
chamber design. Be aware, however, some ELs were released with hybrid engines
using an AU-spec small-port head.
By far, the best head is that fitted to the EF/early EL. "The EF head makes
good power in standard form and, when you decide to go further, they’re easier
to port," says Jim.
Valve sizes went unchanged except the EF XR6 and AU received 2mm larger
exhaust valves. Inlet valve size cannot be increased due to space limitations.
Regardless, Jim says there’s no gain in fitting bigger valves unless the engine
is already modified in a big way.
Since the EA was introduced with an 8.8:1 compression ratio, the Falcon has
received more compression in almost every model.
But Jim says there’s a big difference between the claimed compression ratio
and the actual (measured) compression ratio. For example, the AU engine is
supposed to have a 9.6:1 compression ratio but J.M.M.’s measurements reveal its
closer to 9.35:1...
Either way, the AU’s factory compression ratio is very high for design of the
Jim says their in-house performance-built engines usually go out the door
with a compression ratio of less than 9.55:1 – and that’s an engine built for
premium unleaded only! For use with normal unleaded, Jim prefers to keep to
around 9.2:1. This can vary depending on ignition timing strategies and the
other modifications made to the engine.
The bottom-end of the Ford 3.9/4.0 is plenty strong.
From EF onward, the 4.0 uses hypereutectic pistons, which enables tighter
clearances and improved durability. AU Falcon pistons use a shorter skirt and
are lighter. The 3.9 EA and EB use cast aluminium pistons which aren’t as strong
as those used in later models, but they are nevertheless tough.
Rods are durable, the crankshafts are not prone to failure and the blocks are
rigid enough to make in excess of 300kW at the back wheels (so long as there is
no detonation present).
EEC-IV engine management systems were used on the Ford six until the release
of the EF Falcon. We’re told EF-onward Falcons use an EEC-V system featuring a
knock sensor for more efficient running.
Interestingly, the knock sensor strategy varies across different models.
In EF and EL Falcons, the knock sensor is used primarily as a failsafe for
when you encounter bad fuel. The knock sensor is relatively inactive and, when
necessary, ignition timing is progressively retarded.
According to J.M.M., the knock sensor is much more active in the AU Falcon.
The ECU is constantly adding and removing ignition timing under direction of the
knock sensor. Unfortunately, the ECU is quite slow and the knock sensor is prone
to picking up engine noise.
"The AU computer also takes out 10 degrees of timing in one hit. The AU is
prone to detonate with its high compression ratio – especially with a bad tank
of fuel – and you can feel the knock sensor pulling out big chunks of power,"
says Brendan Mock.
Note that in Falcons with a distributor (all models except EF and AU), it is
easy to rotate the dizzy for a couple of extra degrees of advance – so long as
you run the engine on high-octane unleaded. Early models with low compression
will tolerate considerable advance, but EL Falcons (at about 9.3:1) are
J.M.M.’s in-house Falcon kits incorporate an adjustable fuel pressure
regulator in conjunction with an unaltered management system. Their approach has
been to make mechanical alterations that are well suited to the management
system – not to modify the management system to suit.
An interceptor (such as a UniChip) can be fitted to the Falcon and Jim says
it’s possible to pick up improvements in power and response. The amount gained
depends on the factory program - for example, the AU XR6 VCT program is
apparently pretty bad so it’s possible to make sizeable gains with an
Once you’ve modified a Falcon to go hard you’re unlikely to encounter any
The factory automatic and 5 speed manual gearbox is very strong. Even the
standard clutch can cope with an engine making around 160kW at the wheels. The
tailshaft, axles, universal joints and bearings are all up to the task.
Improved suspension, brakes and performance wheels and tyres are recommended.
Power and Performance
So how much power can a modified Falcon make in comparison to a stocker?
Well, as a guide, standard EA MPFI 3.9 makes about 88kW at the wheels and you
can expect 95 – 98kW ATW in an EF to AU Falcon (including XR6s). The AU VCT XR6
makes about 115 – 118kW.
J.M.M.’s entry-level upgrade (DEV 1) provides more than 112kW at the wheels
using a 2 ½ inch exhaust, headers, new spark plugs and tune. This retails for
DEV 2 adds an air intake, new leads, cam upgrade with adjustable gear and
valvetrain mods. This delivers 125kW ATW at a cost of AUD$2230.
DEV 3 – at AUD$2450 - comprises a more aggressive camshaft for in excess of
A high lift version of the DEV 3 (DEV 3HL) takes the cam about as far as
you’d want to go without performing head work. At AUD$2750 this gives more than
146kW at the treads.
DEV 4 involves cylinder head reconditioning and porting together with more
compression. The price steps up to AUD$4900 but you get more than 160kW ATW.
DEV 5 adds more porting and compression to achieve 170kW ATW at a cost of
AUD$5500. For slightly more power – 175kW at the wheels – you can buy the
AUD$6700 DEV 5a kit which includes special valve springs.
The ultimate naturally aspirated development – DEV 6 – is a custom rebuild
with price on application.
Note that ultra-efficient Race Series headers and other options are also
available – call J.M.M. for details or visit their website (listed below).
In terms of straight-line performance, J.M.M. has a customer car with a DEV 5
kit that runs 14.6 second ETs – with an auto trans and full sound system.
Another vehicle with the same kit has run 14.04 seconds thanks to a manual
gearbox, short ratio LSD and grippy tyres.
So they’re certainly not slow!
When to Go Forced Induction?
In this series we have focussed on the naturally aspirated approach to
performance. But when should you opt for a blower?
Brendan Mock (who owns a supercharged EL XR6) suggests a blower is your best
bet if you want more than about 220kW at the wheels. A supercharger kit along
with a suitably rebuilt engine is the best way to go if you need all-out
Jim recommends avoiding superchargers mainly due to legal reasons. There are
also servicing and engine life implications.