Ok I did research ect.. so many mixed options so I thought I would get a clear answer.

What EXACTLY do I need for my 99 3.8l v6 to make it a 4.2L and what all needs to be done.

Thank you!

 

the easiest way is to find a 99+ f150 shortblock....

but you could change all the internals (crank,pistons,rods)

 

So, the 99+ Mustang heads and such bolt right on too the F-150 shortblock?

What are the gains with just the F-150 shortbock? (with a 99 Mustang, not mine)

 

yes the heads will bolt on....and im not sure of the number gain but it is a noticeable difference

 

Ok, and does it use the same Computer or the F-150 or does it need a tuner?

Any good links out there on the swap?

 

you will need a tune...trust me. i learned the hard way

 

So, I just replace my shortblock with the f150's and get the tune?

What else would you recommended switching, say if I could find a complete f150 motor?

 

I've been asking this question a lot lately. And from what I heard you can only get a 4.2 crankshaft and that will make your motor 4.2...or I might be wrong!

 

Yes, and you also need a 01+ 3.8 oil pan, 01+ harmonic balancer, and 01+ flywheel(or a neutral balanced one). Reason being that the 99-00 3.8 motors are balanced on the flywheel and harmonic balancer, 01+ 3.8 & 4.2L's are balanced on the crank which require different flywheel and harmonic balancer. The oil pan is needed to clear the taller mains of the 4.2L block.

The shortblock is really all that is useful from the 4.2L motor. The cam is less aggressive, and the intakes are way too tall to fit under the stock mustang hood. I think the heads might flow slightly better, but i honestly don't remeber.

 

i thought the 4.2 cam was a little more aggressive