Help Swapping A 2003 4.6 Romeo Into A 1999 With A 4.6l Windsor 5 Speed

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Jeremy Livingston said:

I know that 1999 is a Windsor and the 2003 is a Romeo and needs the intake and accessories off the 1999 to be complete.

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^^^This is not exactly correct. Use the intake manifold from the 2003 even if the 2003 originally came from a Panther (Crown Vic, Grand Marquis, or Town car).

If the donor motor came from a Panther, THEN you will need to use the Mustang upper plenum, throttle body, and air tube. Regardless keep the lower intake manifold.

For the record, I drive everyday a 2000 Mustang that currently has the motor from a 2003 Grand Marquis with almost 100k miles since swapped.

One of the first questions you need to answer is 10.5" or 11" clutch as this will drive the choice of flywheel.

The 11" has better holding power but the clutch is more expensive. If going this route, get a flywheel from a 2001+ Mustang. I chose an 11" LUK clutch because I wanted a car as close to stock as possible.

The 10.5" clutch is cheaper and easier to find. If going this route, get a flywheel from a 1998 or older Mustang.

Check car-part.com for some sample prices of salvage yard flywheels. If you get a new clutch it should come with a pilot bearing.

Parts to swap:

• complete wiring harness. Note, not all of the wiring standoffs will line up. It won't hurt anything.
• fuel injectors, fuel rail, and fuel lines.
• COP's
• exhaust manifolds.
• oil pan.
• oil filter adapter (if the donor motor came with an oil cooler). If you keep the Romeo oil filter adapter it may be necessary to extend the wiring to the oil pressure sender.
• The complete EGR system and all vacuum lines.

You will need to do something with the heater return line. I chose to get a heater return line from a 2001 Mustang. That retained to better O-ring set up on the back of the water pump.

The PCV line will be larger on the 2003. Either figure out some way to join the different size lines or get a throttle body from a 2001+ Mustang.

The location/angle of the T-stat inlet is different. You will need a new upper radiator hose from a 2001 Mustang GT.

If the donor came from a Panther, then there will be a CHT and perhaps a knock sensor. The Mustang does not use these. Either leave them not connected or remove them. Your choice.

Get NEW motor mounts. The Mustang is hard on motor mounts. There will never be a better time to install new motor mounts.

IF the donor motor has more than 100k miles and you are planning to keep this car for awhile, suggest installing a new timing set (chains and guides only). Generally speaking over 150k miles the timing chain is on the decline. There will never be an easier time to install a new timing set than when the motor is on the engine stand.

A Ford service manual and wiring diagrams can be a big help. If interested in getting a copy for yourself I maybe able to help. PM if interested.