I was wondering if i could run an 91+ header on my 1990 4.0. Ive heard different answers. Some say yes, some say yes with some modifications(drilling holes/using old gaskets), and some say NO it won't work.
I do not have an EGR system, the previous owner already removed it. The only thing I'm wondering about is if the sensors will work and if the gasket will seal right because I found a Borla header for 100 bucks on craigslist but it's for a 91+
I have to redo my exhaust anyway because the muffler is crushed and some of the pipe is bent from when the old driveshaft snapped it flailed around and hit the muffler- So I'm just gonna rip out the old exhaust and redo it.
PS I can do the welding and bending that'snot a problem and It doesn't matter if the pipes line up with the old ones Im gonna rerun the exhaust out the back of the drivers side.

 

see if the gasket numbers are the same is 91 still a renix motor or did it stop at 90 and if you could id like to see a pic of you coils where they go to the frame what kind of spacing or custom work is done

 

91 is the 1st year for the high output,so no its not renix,thank god! haha since i have a 91

 

i love mine so simple it makes me smile

 

i heard they r simple but i like the high output part of mine,but back to the OP it should fit,since the only difference is the intake,but please correct me if im wrong

 

Thanks for the input guys, I just wanna be 100% sure before I have my exhaust layin on the floor and buy a new header only to find out it wont fit. I'll snap a pic tomorrow its too dark right now.

 

Here's the only pic I have of the coils and how they're mounted. I has some metal tubing going from the top of the coil to the unibody ant its welded on and reinforced with a couple of tabs. I didn't do the build( although I'll be swapping a Dana 60 in this month) so I'm not 100% sure how it was done.

 

kool on the pic . i just checked at morris 4x4 they call for two different gasket maybe the 91 being h.o. its got bigger ports on the head if the header is cheap enough small ports in to big port header dont see where it would hurt if it was the other way id say no way you can alwas=ys get a bung welded to the header for the renix o2 sensor