Hey, I just bought my first mustang, a 2004 drop top with the 3.9. While looking up an air filter, I found out that Mustangs came with a 3.8 as well, Why would there be 2 V6 engs available and whats the difference if there is any ? horsepower ? milege ? just wondering and thought Id ask a few experts. thanks.

 

and cant answer all that, but i can point out the fact that you will soon realize the 3.8s and 3.9s use most, if not all the same mods.

 

The 3.9L is a slight crank change at the end of the production year. Nothing power or performane wise different.

 

If I recall correctly it was caused due to a parts shortage and Ford started putting a different crank in the 3.8 giving it an extra .1L of displacement.

 

^^Correct.

I believe the 3.9 crank was the one used in the windstar minivans. Due to a shortage (as stated above) they were put in the late 04 sixers.