67 Again: 2006 GT premium, manual

In 2015-16 the Shelby GT350 arrived on the scene and all the talk was about the flat plane crank VooDoo V8 rated at 526 hp out of a naturally aspirated displacement of 5.2 litres.
Just a tick over 100 hp per litre with a high flowing 8250 rpm redline.
Note: These advertised numbers from Ford are based on using 93 octane fuel.

I followed that story closely, like many others, and it got me wondering if I could get a similar result out of the 3 valve 4.6 V8?

So, after doing some research on parts that could contribute to that goal and conferring with Joe Dasilva, in 2017 I went ahead with the most radical mods to the car yet.

The plan was to do ported heads, a big cam and incorporate Ford Racing’s open plenum, high flow intake manifold.
A manifold similar to the Cobra Jet or Boss manifolds of the 5.0 litre generation but made for the 3 valve 4.6.
Since this intake relies on higher rpms for power, the rpm redline would be bumped up to 7500 from the 6000 factory setting.

To support these high rpms, a high volume oil pump by Melling was added, along with more oil reserve from a Moroso baffled oil pan with an 8 litre capacity.
This was required to ensure the overhead cams and valve train would not starve for oil at those higher rpm’s.

By then, ported heads from Ford Racing for the 3 valve were no longer being sold.
So I bought heads from a local salvage dealer off of a recycled Mustang.
I had the heads shipped directly to Dasilva racing and they, in turn, shipped them to Livernois Performance, in Detroit, for porting.
Livernois is the contractor that used to port the heads for the 3 valve for Ford Racing, and still does contract work for Ford Performance.

These heads went in with ARP studs for a long lasting and strong build.
The old Hot Rod cams were replaced by Comp Cams stage 3 cams for naturally aspirated applications.

Because this Ford Racing intake manifold is taller than the OE manifold, the strut tower brace had to be removed.
I tried a V6 brace and it also was not tall enough to clear the new manifold.
I then tried a Boss brace and it was tall enough but it would not allow the hood to close.
So the car is without a brace now.

The performance results of these mods was expected to net another 50 additional hp, and it did.

The dyno results showed 456 hp on a 91 octane tune and 458 hp on a 93 octane tune, like Ford’s numbers.
Just a couple hp short of the 460 goal.

And, like the GT350, I wanted to remain MVI compliant by retaining catalytic converters, which I did.

So the goal of 460 hp is realistic.
Deleting the cats would do it by itself, adding 4 or 5 more hp.
An electric water pump would also do it by adding 2 or 3 more hp.
Lighter wheels could do it too by returning another 2 or 3 hp.

Chasing those last couple hp is not a priority.
I’m satisfied with the achievement.
And since the difference between 91 and 93 octane was so small, and the fact that we don’t have 93 octane in Atlantic Canada, I run the car on 91 octane.

The exhaust note has become a bit more present than before, but not by much.
And, the look of the engine bay changed with these mods.

Here is what it looks like now.

View attachment 56575
I've got a couple more ideas for mine . Thanks for the very detailed and informative write up Marc...
Ok, so the last round of mods really changed the way the car pulls.

The biggest reason being the intake manifold.
It is a short runner intake as opposed to the stock manifold which was a long runner intake.
5” inch runners as opposed to 9” inch runners.

Difference between is that long runner manifolds are good for low end torque but not good at supporting high rpm power, while short runner manifolds don’t make so much low end torque but are better at making high rpm power and for longer up the rpm scale.

Example: the stock manifold hits peak torque a good 1000 rpm sooner than short runner, and only makes power up to 6000 rpm, then falls off fast beyond 6000.
On other hand, short runner intake does not make as much low end torque but keeps making power up to 7000 rpm, and past that does not fall off, just plateaus but keeps pulling.
This is the reason the rpm redline was moved up to 7500 with the support of the new oil pump and larger oil pan.

Feeling wise, there’s not much excitement bellow 3500-4000 rpm with the short runner intake, but at 4000 there’s a noticeable and almost violent surge of power that comes on and keeps going all the way to 7500.

For dirt bike or snowmobile enthusiasts, it’s like a 2 stroke engine when the power band comes on.
Or like a mini power adder kicking in, turbo or supercharger.
It’s a rush.

There really is not much to the bottom end.
So to make it work, you have to adapt the driving style.
You ride each gear longer to get to the high rpm’s.
It makes noise and it develops velocity.
Like having to visit Mexico often and regularly.
Think street legal race car.

To get to the high rpms more quickly and be in the power band sooner, in 2018, I upgraded gears again to 3.90’s up from the 3.73’s I had been running for several years with the previous setup.
This was a good improvement, helping get to that 3500-4000 transition zone more quickly.

So, for real world applications, each time one gets going from a stand still, your car goes from idle through 1000, 1500, 2000, 2500, 3000, and so on…
And with the stock manifold it makes good torque and useable power through that whole range.
And a lot of people don’t go much passed 4000 or close to.
So you use the full potential of the stock intake every time all the time.

But how many get to 5000 or 6000 rpm and how often?
I’m sure not nearly as much.
Seeing as the short runner intake only really comes alive around the 3500-4000 rpm mark, a lot or most driving scenarios don’t or would not exploit its capabilities.

So, for a lot of applications it would not be the right setup or money spent in the right place.
It could leave some individuals disappointed.
That manifold really needs to be part of a complete build with all the supporting mods.
I really would not recommend it by itself on a mostly stock engine.
So, I combined a trip to Pickering for the 3.90 gears in 2018 with a HPDE track day at Mont TremblantI on the way back.

Since I was heading to the track, I did new Baer 2 piece slotted rotors with aluminium hats, Hawk HPS 5.0 pads and fresh synthetic DOT 4 brake fluid.
My old rotors were still good but the hats on the one piece rears were rusted and I was tired of looking at the rust.
I also did a plus 1 rotor increase in the back to manage heat.
Maybe at the cost of some acceleration because of the larger rotor, but the aluminium hat versus the all steel one piece pretty much evened things out weight wise.

Here is a shot of the rear end waiting on the new gears.


Here are the front and rear rotors.



Also, since I lost use of the strut tower brace the year before, I installed a Steeda trunk X brace to re-add a bit more chassis stiffness.
It ties the tops of the 2 rear shocks to the chassis top of the trunk behind the rear seats.


And I did some more weight reduction by pulling the spare wheel, jack and hardware since the spare would not fit over either the front or rear brakes now.

I also pulled the windshield washer reservoir since I never use it anyway.
That is 9-10 lbs of fluid when full.

Also, since I had not turned the radio on in 5 years, I pulled the radio head unit and all speakers.

All added up, this was good for another 70 lbs of weight savings.

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Well broke out the green monster this morning.
Drove it to work and had oil change done and alignment checked.

I hope we can say holy crap on this forum.
Because “holy crap” is that car fun to drive!

I forget from year to year, but man it’s a thrill.
Despite what I said above about the intake manifold taking away some bottom end, what a thrill when it hits that 4000 rpm mark and opens up.
Both in velocity and sound.

It’s a manual, so you keep the rpms in the range with gear shifts.
I call it keeping it on the boil.
It’s not a torque monster so if you want to go, you rev match, drop a gear, bury your right foot and enjoy the experience.


Ok, so here is the laundry list of mods done to 67AGAIN.

**Engine and powertrain:
AC delete with Ford Racing pulley
Granatelli Motorsport crank and water pump underdrive pulleys
JLT series 3 CAI
FR twin bore 62mm throttle body
Livernois Motorsport ported heads
Ford Racing open plenum, short runner, intake manifold with charge motion delete
Comp Cams stage 3 cams for NA application with Ford blue valve covers
BBK long tube headers with high flow catted X pipe
Maganaflow Magnapack wide open exhaust
Hurst billet short throw shifter
Axle Exchange one piece aluminium driveshaft
Motive gear 3.90 gears with FR vented diff. cover
JLT driver side oil separator
Windshield washer reservoir delete
91 octane SCT custom tune by Matt Dasilva from Dasilva Racing
387 WHP on 91 octane tune
389 WHP on 93 octane tune

**Suspension and chassis:
BMR LCA's and relocation brackets
BMR adjustable panhard bar with Steeda panhard brace
Eibach front and rear sway bars
Ford Racing “P" springs, 1" drop
Bilstein HD shocks and struts
BMR K member brace, A arm support
Whiteline K member to rad support brace
Maximum Motorsport caster-camber plates
Steeda shock mount to chassis X brace
FR Brembo GT500 front brakes with Goodridge SS lines and Motul DOT 4 full synthetic fluid
JLT front brake cooling ducts
Baer Eradispeed 2 piece slotted rotors with aluminium hats and plus 1 rear rotor size
SVT 18" wheels with 255/45 front and 285/40 rear Good Year Eagle F1 tires
Spare tire, jack and hardware delete

MRT 67-68 replica hood
Silverhorse Racing flush mount quarter window louvers
OE V-6 spoiler for more of a fastback look
'08 Bullitt grille with Raxiom 60's style headlights
GT fender badge replaced by tri bar pony
60's style rocker stripe

**Interior and Function:
FR Recaro "Boss302" seats
Radio and all speaker delete
A few Silverhorse Racing billet pieces
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I feared I was going to forget something on the final list.
And I did. ?

So far, I forgot:
Melling high volume oil pump
Moroso high capacity baffled oil pan with 8 litre capacity
ARP studs used to bolt the ported heads in

I hope I got it all now. ?