[shelbycobra]

my car has 117,000 miles on it, and im thinking of either getting a new 4.6 or have mine rebuilt,but will the 5.4 fit in my cobra too,i read somewhere that some of the cobra r and saleens had 5.4 in them and had plenty of power.please help with advice.

[Mana4Real]

Yes it will. I don't know how hard the transplant is though.

[GTRaptor]

The new 5.4 3 valve engine in the Ford trucks would be a nice transplant, you wont be able to use DOHC heads though.
You will need a cowl to make it fit, since the deck is taller. The truck manifold is more geared towards the low end, so porting it or switching to a FRPP or aftermarket manifold would be a wise move.

You can use ANY 4.6 manifold in a 5.4 provided you make some spacer plates that match the head ports and extend the size of the 4.6 intake (to compensate for the wider separation between the heads).

This has been done before with 5.4 SOHC 2 valve engines, 5.0 Mustand and MM&FF wrote articles about this swap.

Is it a good move? tough question.

The Cobra engine is pretty capable, with the right combo of parts it can be a screamer NA, Supercharged or Turbo.

I think it is a matter of how much and where do you want to go.

If i were you i'll stick with the DOHC engine and rebuild it with forged internals and either go NA or with some form of forced induction. I think this will be cheaper than going to the 5.4 and test-try different things with it, there is definately more guessing involved.

If your car was a V6 or a dying GT i would consider the 5.4 option as the better alternative. But you already have a great foundation to build up.

The 5.4 transplant could also make your Cobra loose value.

[Flex]

Agree with Rob totally. Stick with the original motor dude.