I am considering installing a 5.4 short block in place of my 4.6. I am wondering if anyone out there has done this. I know the engines are in the same family, but I am looking for details before I spend money. I have been told that the 4.6 heads are different than 5.4 and that it would raise compression to use them, I use this vehicle to tow and I need more torque, but I still want to be able to use regular fuel, not premium. I seem to be having trouble getting any solid answers on what I will run into. Things like will the same injectors run the 5.4, will I need to get the PCM reflashed, etc. I welcome any questions, comments or ideas.
thanks
tom

 

Welcome to FTE. Although I have a 4.6 and know a few differences between that and the 5.4, what I know wouldn't help what you are doing. If no body here knows anything more than I do, possibly the gurus in the 4.6 - 5.4 enging forum would know better. Good luck with it.

 

I have browsed some of the other post, found some useful info, but not enough to satisfy me. Does anyone know of any books or publications that list engine specs and blueprints of the 4.6 and 5.4 engine families?

 

5.4 and 4.6 heads are identical, if they are both NPI or PI, in which in your case for a 98, they are NPI. If you put PI heads on a NPI shortblock, then yes the CR goes up (from about 9.1 to 10.5ish on a 4.6) in which premium fuel is needed. You would need a different intake for sure since the 5.4 is wider than a 4.6. I would suggest getting a complete motor, you could always part out or sell the other motor. Injectors are the same, 19#ers, not sure on MAF, but I would assume it would be the same. You would need a tune for the 5.4 swap to run on the 4.6 eec, unless you swapped out the eec's and wiring as well. I think a chip/tune would be much easier.

Joe