4.6 to 5.4 ENGINE SWAP

[marc soto]

I Have an F- 150 with a 4.6 I want to swap to 5.4 what is involved do i need new wire harness or can i use the same from 4.6 how about mounts .I just need as much info as i can before i open a can or worms. Thanks NMRA :confused:

[chag]

Well Mark, depending on the year of your truck and what you want to change will make a difference. If just a straight engine change, then it is not to much of a problem. My advice to you would be to get a PI 5.4 engine from 1999 and up. Better Power. If you want a little better torque, use a 97/98 short block with the 99 or newer heads for about 3/4 of a compression increase with the 99 0r newer intake. You will have to change the exhaust Y-pipe to fit the larger 5.4 engine. Now you didn't say what year your truck was.If it is a 96 to 98, it has a return fuel system and its' own computor. In these years, the 4.6 came with a 4R70W tranny(the really good one, and lighter) and the 5.4's came with the 4R100(what ever they call the big c-6 derived OD tranny). If your truck is 98 or older and you want to go the 5.4 route, the 5.4 will bolt on using the mounts, the flywheel, and you'll have to check on the exh. manifolds, but I know the Y-pipe will have to be for a 5.4. Now, you will have to get rid of the coil on plug set up and use the coil packs and electronics off the 4.6 and just get your computor reflashed to the larger motor. It will run on the 4.6 program, just be a little lean.Why use the plug wires on the 5.4? Well, Ford never made a computor to run the 5.4 with the 4R70W tranny in a return fuel system. Therefore you would have to change the transmission,crossmember,Y-pipe, torsion bars, and drive shafts if you wanted to use a 5.4 calibrated computor.
If your truck is 99 and up, Ford started using the 4R70W tranny behind the 5.4 motor, but they also started using stupid idea of a none return fuel sytem and shutting down and cycling the fuel pump to control the fuel pressure. This design has its' flaws. Anyway, You will be able to get a computor to run a 5.4 and 4R70W tranny with this fuel system and plug on coil that the 5.4's come with. The 4.6's started using the coil on plug also, but not sure when in the trucks.
I was involved with someone who did it the hard way in a 97,by changing everything. Not cost effective, but we sure learnt alot. It was worth it, but I personnally would stay away from the 4R100, as I feel the 4R70W is a far better tranny and much lighter. We have one here that is kicking over 335,000and had nothing but regular oil changes.Mine has 183 on it. My tranny guy is a Chevy guy, and admits he doesn't see many 4R70W trannies, and they are high mileage or just plain abused and no maintenance. And by using the coil packs, you can get aftermarket coils and wires that make great power cheaper then buying after market coil on plug coils. Anyway, hope I didn't scare you. It can be cheaper and more satisfying then buying a new truck. And when the the motor is sitting in the stand you can install cams very easy. Just remember the intakes are limited to under 5000 or so rpm's. Good luck!!..Karl

[marc soto]

thanks karl this info will help out a great deal

[marc soto]

hey Karl is there a phone were i can call you and ask you some questions you can email me your number to speedracer1260@aol.com thanks