I have a 2003 F150 4.6L V8, automatic 2WD. I need to get new cylinder heads put on it but I was told it may be cheaper to just get a whole new (new or used) engine put in it. What other kinds of engines could I put in there that would be compatible without having to change the transmission?
Thanks for your help.

 

A 5.0L should bolt up. The problem your going to have is that any engine other than a 4.6 is going to need a standalone computer to shift the transmission (they aren't just simple auto's that rely on hydraulic pressure and a kickdown to depend on when to shift anymore). I have met a couple of guys who went to Cummins 4BT diesels for the torque increase and that it bolts right up to 4.6 and 4.2 transmissions. It's the mechanical 5.9 found in Dodges from 88-97 minus the front two cylinders creating a 3.9L I4 that makes 150hp and an easy 350 lb-ft but can achieve up to 30mpg. You ditch computer control (except the transmission) for the most part and just have to swap sensors to get the tach to work (need this for cruise control), water temp, oil pressure, ect. For your purposes, its probably just easier to replace the heads (aftermarket performance heads would work as well) or another 4.6.

 

I would go with the 4bt it might be a little work but it would get a lot better fule mpgs

 

nope. The 4R70W will not bolt to a 302 block.

 

Really? I know my M5R2 will bolt up because some of the Broncos the had the 5.0 with the M5R2. The 4.2 and the 4.6 had the same transmission options for the most part. Wonder what exactly is different. The 4.6 had the M5R2, and then two automatics, right? The 4.2 had the M5R2 and one auto option. Interesting.

 

the 4.6L had two options, an M5R2 and 4R70W. The bellhousing on the two transmissions are matched for the block.

 

you should swap in a disel or a 5.4

 

The M5R2 will bolt up to a 302. It was behind some of them from the factory...

 

the M5R2 from a 4.2L will, the M5R2 from a 4.6L will NOT. Why is this so difficult? transmissions from modular motors will NOT work with other blocks.

 

Forgot the 4.6 was modular. Used to dealing with a 283 from back in the day.