3.9 / 4.0 heads/?? for headers to work.

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Author Message   Mike Shoemaker (Shoe) New Member Username: Shoe Post Number: 16 Registered: 05-2003 Posted on Friday, October 10, 2003 - 02:55 pm:    Does anyone know for sure if the heads for a 3.9 are the same for the 4.0? And if the Australia RHD is different the the US LHD? This would apply to the factory exhaust manifold part #'s. If they are the same I will be getting new headers soon. Thanks Shoe   Ron Brown (Ron) Senior Member Username: Ron Post Number: 495 Registered: 04-2001 Posted on Friday, October 10, 2003 - 04:00 pm:    from an exhaust manifold point of view they are the same. The issue is that the headers that clear on RHD do not necessarily clear the steering on LHD. BTW don't forget you have to mate the y pipe to those headers. Ron   John Houseman (John_houseman) New Member Username: John_houseman Post Number: 20 Registered: 02-2003 Posted on Friday, October 10, 2003 - 06:00 pm:    Neither the australian or rpi headers will work on an NAS 4.0. Interference with the steering for both and also ds knock sensor with the rpi. Don't get me wrong they'll bolt up but I wouldn't suggest either for a 4.0 unless you like driving with that little yellow light on and having lees performance than when you started. The rpi will work with the 3.9 only bc it has no knock sensors. Also on the 4.0 the rpi y pipe has no provisions for your after cat 02 sensors. Your steering shaft will rub on one of the mandrels as well, could create problems long term. IMO it seems alot of us are focused on new exhaust ss headers blah blah blah, I was once there myself. The fact of the matter is that for all the money and trouble (overseas shipping cost phone calls taxes etc) all this creates and the end result being barely noticeble to minimal why bother. I could go on but why bother. Just tryin to save someone else from making costly mistake as I have. For what it's worth, my suggestion, concentrate on the intake side of the spectrum not the exhaust.   Mike Shoemaker (Shoe) New Member Username: Shoe Post Number: 17 Registered: 05-2003 Posted on Saturday, October 11, 2003 - 12:42 pm:    Thanks. These were the concerns that I had to. I all ready have a 4.6 engine so power increase from headers are not a big issue. I was just try to find something that would bolt on easy for a possible better fix the the stock manifolds. Thanks again Disco Web!!