2003-2004 Mustang Mach


2003-2004 Mustang Mach 1 Eaton Swap Info

There are many of these units available for as little as $400 due to the KB and Whipple upgrades to 03 Cobras. At first glance it seems like a low cost way to boost your N/A Cobra or Mach-1, when in reality its very expensive to get all the parts together ($7000+ and more like 10,000+ if you do it right and forge your bottom end).

Not to put down those with the ability to fab things up, but in reality picking up a $400 Eaton and fabbing up some sort of drive system is really not doable, you are talking about 6500+ RPM and the system needs to be very well engineered.

That leaves things to trusting Ford and just converting to the 03 format and just bolting everything on (and it's just that simple, it's pure bolt-on for 99.9%of this upgrade). Just educate yourself of how many parts it takes to complete this bolt on, and how little of those parts are included in your typical E-Bay auction.

You can also purchase an 03 motor, many can be had for $7500 to $9500 and in most cases include a T-56. In many cases you can slide in this new forged powertrain for less than the cost of converting your existing non-forged block to the 03 format.

I found a unique auction (and it was not your typical Eaton removal for upgrade), someone had actually trashed an 03 motor so they removed 100% of the parts (except the timing cover & trashed heads) from that motor and I won the auction for $2500. I had every nut, bolt, clamp, coolant line, vacume line, and upper/lower engine harness wires needed to convert to the 03 format. All I had to buy was an 03 timing cover, 03 heads, and an 03 oil cooler. Even with all those parts, in the end my All Alloy Terminator conversion ran $14,000. I did add every upgrade I could but even if I went pure budget this conversion would still have cost about $8000.

Mach-1 and 99+ conversions are least costly because you already have C heads and with the Mach-1 you alreay have 03 Cobra heads. Still it's a costly venture. In these cases you need the 03 timing cover and all accessories, and all the top of the motor parts, and all the intercooler parts, and it can be done with the motor in the car. You end up with a non-forged 03 motor that should stay at around 6 to 8 psi (maybe an 80HP upgrade that costs you $5000+).

Here is a general list of what you need to convert your 96-98 short block to the 03 format (99+ Cobra and Mach-1 folks just delete the heads). I'm flowing visually as a molecule of air getting sucked in through the air filter and flowing through the motor:


03/04 Cobra Plastic intake parts (or aftermarket 03 CAI).

03/04 Cobra 90mm MAF (or LMAF, or SCT Big Air or other aftermarket MAF).

03/04 Cobra TB (or Acufab or other aftermarket TB).

03/04 Cobra inlet plenum (comes with Acufab if you go that route).

03/04 Cobra Eaton M112 (get a ported one if you can).

03/04 Cobra Intercooler w/metal water line fittings, o-rings & attachment bolts. Also for this system: intercooler pump, bumper mounted heat-exchanger, plastic resivour, and all connecting lines.

03/04 Cobra lower intake manifold, metal gasket to Eaton & attachment bolts, gaskets to heads and attachment bolts.

03/04 39lb injectors, or 42lb Bosh injectors (42lb Bosh will mate to your existing 96-98 harness, 39lb will mate to your 99+ harness)

03/04 fuel rail (96-98 owners need to spend more money in this area, you actually need to convert the 03 lower manifold to work with a return style fuel system. You need aftermarket fuel rails, fuel pressure regulator, and all the lines and fittings to connect it all up, runs about $700 if you include the intank 255LPH pump).

03/04 Cobra Heads (or any 99+ "C" heads will also mate to the 03 lower manifold). You will also need new head gaskets (I suggest MLS) and new head bolts as you cant reuse Ford TTY bolts. I suggest an ARP stud upgrade.

03/04 Cobra exhaust manifolds required if changing to 03 heads (they have larger more squared off exhaust ports).


03/04 Cobra timing cover (costs about $465 through Ford, comes with new front seal and idler pully on drivers bank). If using an aluminum block one bolt hole does not line up and all you do is leave out the bolt and RTV in that area.

03/04 Cobra harmonic balancer (has threads to accept the 8-rib 03 Cobra supercharger drive pully)

03/04 Cobra 8-rib supercharger drive pully & mount support & bolts.

03/04 Cobra Alternator (has 8-rib pully), 2 mounting supports & bolts. You also need the 03/04 alternator 3 wire electrical connector (just splice it into your harness).

03/04 Cobra upper pully assembly, has idlers and tensioner that guide/route the 8-rib supercharger belt).

03/04 Cobra 8 rib supercharger belt (or aftermarket belt sized to work with your combo if you have elected to change your S/C pully to a smaller size like 3.1, 2.8, or 2.7)

03/04 Oil cooler (it will mate to your existing oil cooler flange).

03/04 coolant crossover tubes (you will need to add 1 extra water temp bung for your 96-98 computer, and another bung if you want to add a water temp gauge).

03/04 coolant lines and thermostat housing assembly.

You can reuse your A/C compressor, P/S pump, and water pump as these 6-rib units will work with the 03 timing cover system. You will have to bend and tweak your P/S lines to get it to work.

Tuning: you need a tuning system for your 96-98 or 99+ computer: I suggest SCT racer tuning software @ $850. Or get a mail order chip, but be prepared to pay $1000+ to have someone dyno and re-burn your chip to tune & tweak your motor to perfection. NOTE: Full conversion to the 03 computer requires use of an 03 instrument cluster (has digital odometer) which means changing the entire dash harness.

Gauges: you need Boost, Fuel Pressure, and Wideband 02.

Ignition: you will need a Boost-a-Spark or MSD system.

Fuel: If gong with a 2.8 pulley you will be at 450ish HP and you will need to look at upgrading your fuel pump. For 96-98 return style systems a $90 Walbro 255LPH pump is the best choice.

Bottom End: the stock M112 Eaton with 3.5 pulley will get you around 8 to 9psi. If you stay with your stock non-forged bottom end you MAY be OK. I firmly suggest if you are spending $5000 on these parts to go ahead and forge your bottom end with Manley H-Beams, ARP 2000 rod bolts, and JE or Diamond Racing forged pistons. Then you can go with a 2.8 S/C pully and get to 14psi @ 465+ RWHP.

In closing:

Buy SHM's how to build Max Perfomance 4.6 motors, it's really a good resource for 4.6 101 questions and understanding many details about Cobra motors.

Look at the exploded Terminator motor pic in my website (E-Mail me for a copy you can zoom in on), study and learn about all the parts I have been talking about.

Write Up By:

Bill in Denver



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