FOMOCO466

Looking for incite. . 98 5.4 going into 03 expy with a 4.6. Looking to do this for wife's cousin. Her 03 Expy has over 260k on the clock.. uses oil...runs rough.
Got a 98 5.4 with 102k miles on it all maint documented. What is the biggest issue I am going to face? Will the 4.6 comp work? Can I get a 5.4 comp and harness from a 04 and plug and play? The old 4.6 is a 2v also..
Any input is appreciated.

97badass

You will have to extend some wires and change the exhaust to the 5.4 and have the tune changed

FOMOCO466

So a 5.4 harness would be better.. is sensor position the same for both? So 5.4 harness and ecu and 5.4 manifolds... or piping change...

FallGuy44

I could be wrong, but I remember reading something about the transmission. So be sure to research which trans you have and if it can handle the swap to a 5.4.

Fordfan2006

torque converter from a 5.4 also.

Jbrew

Keep the 4six harness, PCM, lengthen the IAC harness (2 wires no biggy), = plug an play basically. It'll be drivable without a hitch.

Numbers are about the same, close. Just run it up to the dealer and they'll correct the shift points.

Keep the 4six heads, they out flow the 5fours and are a direct fit. Something you can do in the future IF the heads are in good shape. If you go that route someday, you'll need a 99+ intake manifold before you can make that happen.

FOMOCO466

I have the complete 5.4 manifolds to pan.. its a 98/99 model.. just like my 99 eddie bauer.

97badass

The torque converter thing is bogus, all it does is gives you a little bit higher stall speed. It's not going to blow the transmission up just because you have a higher stall. Otherwise my racecar should have blown up instantly with a 4000 stall....

97badass

The 03 has better heads than the 97-99 5.4 like said. You'd be better off to swap them onto the 5.4