12-14-2009, 08:39 AM
NTIman Wrote:I just feel like that the modular engine was a great engine, but never reached its full potential (especially in the aftermarket) because of heads that never reached the full potential of the engine.
This is somewhat true if you're talking about the 2V version of the 4.6 and 5.4 used in many base models. This has more or less become a non-issue with the introduction of these heads. Not to take away from the Mustang GT, but usually for serious performance applications a 4V is preferred.
The 4V variant of the 4.6 used in the Cobras never really had any breathing issues that were caused by the heads, thus the lack of aftermarket offerings to date. Most of the bottle neck on those early cars ('96-'98) was due to the poorly designed IMRC plates and the physical size of the intake manifold/induction piping.
On the '99-'01 Cobra engines Ford dropped the IMRC system and went with a tumble-port head design. Instead of each intake valve having its own runner in the head, the tumble-port heads have a more conventional single rectangular port for each cylinder.
Heads used on the '03-'04 Cobras were an even bigger step up from the tumble-port heads. Based off of the Ford Racing FR500 castings these heads (as cast) flow right around 240 cfm @ .500 in of lift on the intake and 170 cfm @ .500 on the exhaust side. Couple these heads with anywhere between 9-25 pounds of boost and breathing isn't a problem.