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2.5 exhaust manifold


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Ok, I've got an 86 2.5. 2wd. My original plan was to just do minimum to get it driveable while I gather parts to swap in a late model 4.0 and 4x4. The better I get the 2.5 running the more I like it and with current gas prices I'm thinking I'll just stick with it for a while. Anyway, I've got a cracked exhaust manifold. So far everything I'm finding as far as aftermarket Headers go are for 91 up. But Parts store shows same part #'s for 91 O.E Manifold as for my 86. Anyone have any "insider" knowledge that might help?

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I have the same 2.5 issue you do. I posted this same question on NAXJA and got no responses. I too am curious as to how easy or difficult a header would be to put in a 2.5 MJ as there arent any listed for our specific applications. And Ive also seen they only list them back to 91 when they went to port injection. I think the difference might be with EGR, as the port injected models didnt have EGR, and the TBI models did. So with that thinking, if you did away with your EGR, and made sure the O2 sensor was close enough to stock to be able to mount it, I would think there shouldnt be a problem bolting it up, and then making sure that the downpipe to the cat will go in place, or modifying it to do so. I have just been looking for someone who has done it or seen it done to make sure my thinking is right.

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Thanks, more info than I had... lol. Oreilly's down here shows the same part # on O.E manifolds for 86 as 91. I'm not worried about making the cat or exhaust pipes work, I'll probably cut the cat out anyway. I just don't wanna drop the coin for a header then wind up having to cut and patch it.

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I've had a set of pacesetter headers part number 70-1137 (on ebay for 170.)for the 2.5 wrangler laying around waiting to be put on my 86 2.5 (just moved to CA and gotta smog it first). I chose the pace setter header cause of the long primary tubing. There are shorter primary headers that may bolt right to existing down tube like clifford performance. From what I have seen is all the 2.5 manifolds 95 and prior are the same so the headers will bolt up to the 86 head but there are some small problems that i have seen with the pace setter but nothing serious. From what I can tell you will lose the egr, then the o2 sensor will b located further down the exhaust so some wire splicing will need to be done, then the power steering bracket will need to be trimmed a little, and the down pipe comes a inch or two short of bolting up to the catalytic converter. Just a little exhaust fabrication will take care of that. I will post some pics and problems when I do it soon.

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Ive gutted and sleeved the cat and installed a flowmaster muffler on my 2.5 with NO noticeable loss of low end torque, and did gain a small amount of power felt in the seat. I can't see how the change from a manifold to a header is going to make any loss of torque at this point. My plan is to rebuild a spare 2.5 I have with some power adding mods..... port and polish, cam if I can find one, and go to maximum overbore with the cylinders, maybe see if I can make a 2 bbl throttle body work with the existing computer system... stuff like that. I know that to many of you it all sounds pointless, but I see it as more fun this way, as I really don't need the power that a good ole 4.0 has to offer. And.... up to this point, I havent had a 4.0 donor fall in my lap, so, I have to work with what I have. So, when the time comes, I will have a header!

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Manifold design can greatly affect the way your engine delivers power,

If you already gutted the cat and added a high flow muffler the manifold is the only thing creating backpressure removing the backpressure could move up the powerband and hurt torque. The truck might feel faster due to the increase in top end but in a 4X4 your after low end grunt.

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The best bang for your buck is a header, exhaust manifolds are used because 1 they are cheap to make 2 to lower exhaust noise 3 exhaust scavenging (or lack there of) for emissons. Anyway it comes down to what you are doing with your truck, if this is your daily driver Id recommend getting rid of the manifold as long as you don't have to get emission checks every few years. If youre worried about torque and still want a header just get a shorter primary. Google this...... Banks header GBE 51316 This one costs more but it maybe a better of both worlds kinda thing.

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